No. 120,371

IN THE COURT OF APPEALS OF THE STATE OF KANSAS

COOPER CLARK FOUNDATION,

On Behalf of Itself and All Others Similarly Situated,

Appellees,

v.

OXY USA INC.,

Appellant.

SYLLABUS BY THE COURT

1.

Under Kansas law, all gas leases impose an implied duty on the gas company (the 

lessee) to market any gas produced from the well. Unless disclaimed by express 

language, that means the gas company must market its product at reasonable terms within 

a reasonable time following production.

2.

A corollary of the gas company's duty to market the gas is the marketablecondition rule. Under that rule, the gas company must make the gas marketable at its own 

expense, which means that expenses required to make the gas marketable cannot be 

deducted from royalty payments. Once the gas is in marketable condition, expenses may 

be deducted from royalty payments.

3. 

The concept of marketability is tied to the market for the gas. When the parties 

have agreed that the gas will be sold in the interstate market, the gas company cannot 

deduct expenses required to make the gas marketable for the interstate market.
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4.

When the parties have agreed that the gas at issue will be sold in the interstate 

market, that some of the gas produced from the same well could be used at the wellhead 

or at a farmhouse does not make the gas at issue marketable under the marketablecondition rule.

5.

The district court has considerable discretion in deciding whether certification of a 

class-action lawsuit is appropriate. If the court considers the relevant factors listed in 

K.S.A. 2019 Supp. 60-223, the appellate court reviews the decision only for abuse of 

discretion. The district court abuses its discretion if its decision is based on legal or 

factual error, or if its discretion is arbitrary or unreasonable. Factual findings must be 

supported by substantial evidence; underlying legal issues are reviewed independently, 

with no required deference to the district court.

Appeal from Grant District Court; BRADLEY E. AMBROSIER, judge. Opinion filed June 26, 2020. 

Affirmed.

Mark C. Rodriguez and Deborah C. Milner, of Vinson & Elkins LLP, of Houston, Texas, and 

James M. Armstrong and Mikel L. Stout, of Foulston Siefkin LLP, of Wichita, for appellant. 

Rex A. Sharp, Barbara C. Frankland, Ryan C. Hudson, and Scott B. Goodger, of 

Sharp Law LLP, of Prairie Village, for appellees.

Before LEBEN, P.J., GARDNER, J., and MCANANY, S.J.

LEBEN, J.: Oxy USA Inc. appeals the district court's decision to certify Cooper 

Clark Foundation's class-action lawsuit. Cooper sued on behalf of Kansas landowners 

with leases allowing Oxy to extract natural gas from their property in exchange for a 

monthly payment. Cooper alleges that Oxy underpaid landowners for several years by 
3

subtracting processing expenses from payments in violation of Oxy's duties under the 

leases. On appeal, Oxy raises four issues with the district court's certification decision. 

We begin with a preview of those issues and how we'll resolve them.

First, Oxy argues that the district court misapplied a legal doctrine underpinning 

many of Cooper's claims: the marketable-condition rule. Oxy says the court misread a 

case applying that rule, Fawcett v. Oil Producers, Inc. of Kansas, 302 Kan. 350, 352 P.3d 

1032 (2015). Oxy contends that, under Fawcett, the class cannot be certified because the 

district court can't decide whether gas was marketable without evaluating gas quality 

from individual wells. But Oxy misreads Fawcett and ignores the way in which Cooper 

has defined the proposed class. Under Cooper's class definition, the only gas included is 

gas bound for the interstate market. So even if some small amount of gas could be used at 

the wellhead to run equipment or at a nearby farmhouse to provide heat, that wouldn't 

affect the marketability of the gas headed to the interstate market. And only that gas is 

included in Cooper's class.

Second, Oxy challenges the district court's commonality finding. A district court 

can't certify a class without finding commonality, meaning that all class members' claims 

depend on a common contention that's capable of resolution classwide. Oxy says several 

aspects of Cooper's claims present individual questions that should have precluded a 

commonality finding. But Cooper supplied ample evidence for the district court to find 

that the class petition raised several common questions, so the district court was right to 

reject Cooper's contrary claims. 

Third, Oxy attacks the district court's predominance finding. Cooper certified the 

class under K.S.A. 60-223(b)(3), so the district court had to find that questions common 

to all class members predominated over those affecting only individual members. Oxy 

says that its statute-of-limitations defense presents individual questions that predominate 

because the district court will have to consider whether each class member has an excuse 
4

for failing to timely file their claims. But Oxy's defense can be litigated classwide; and 

even if it could not, the individual questions that defense might pose would not 

predominate. So the district court didn't abuse its discretion in finding predominance. 

Last, Oxy claims that the district court failed to rigorously analyze the statutory 

requirements for class certification. Oxy points out that, before certifying the class, the 

district court didn't expressly rule on Oxy's motion to strike Cooper's expert testimony. 

Oxy says the failure to do so violated a requirement that the district court rigorously 

analyze the statutory requirements for class certification. Yet nothing in the substance of 

Oxy's motion would have precluded certification. And even if the district court should 

have ruled on Oxy's motion before certifying the class, the court implicitly did so with 

detailed findings rejecting the substance of Oxy's motion. On Oxy's last argument, like 

the other three, we find no error in the district court's decision to certify Cooper's class 

action. 

FACTUAL AND PROCEDURAL BACKGROUND

We consider the issues of this appeal in the context of how gas is produced from 

the Hugoton Field. That field was once described as the largest reservoir of natural gas in 

the world. It's no surprise, then, that most Hugoton Field gas doesn't stay in Kansas—it's 

sent to pipelines for sale in the interstate market. See Coulter v. Anadarko Petroleum 

Corp., 296 Kan. 336, 339, 292 P.3d 289 (2013); Southwest Kan. Royalty Owners Ass'n v. 

Kansas Corporation Comm'n, 244 Kan. 157, 160, 769 P.2d 1 (1989).

To understand the background of the case so that we can then discuss the legal 

issues of this appeal, we will first review the gas-production process and the gas leases at 

issue. When we get to the leases, each lease has a lessor, the landowner who grants rights 

to extract gas beneath the surface, and a lessee, the gas company that takes the gas to 

market it. For the ease of the lay reader, we'll simply refer to the lessee as the gas 
5

company throughout this opinion. Cooper seeks to represent the lessors in this class 

action; Oxy is the gas company or lessee. 

The production process

This case involves a class-action lawsuit about natural-gas leases. Cooper 

represents 190 Kansas gas wells owned and operated by Oxy until 2014 (Class Wells). 

Oxy produced gas from Class Wells under 245 leases (Class Leases). The leases covered 

wells in the Hugoton Field, which stretches from southwest Kansas down through the 

panhandles of Oklahoma and Texas. 

Most but not all Hugoton gas is bound for the interstate market—a small amount is 

used near the well in its raw form. You can use raw gas to heat a home (House Gas) or 

power irrigation equipment (Irrigation Gas). Or you can use it in the field to power gasproduction equipment (Field Gas). But most Hugoton gas isn't used near the well—nearly 

all of it (about 99%) is sent for processing and sale in the interstate market.

That's what happened in our case. Oxy sent a small amount of gas from Class 

Wells for use in its raw form near the well: gas from 13 Class Wells was used as House 

Gas and gas from 24 Class Wells (about 2% to 3% of all gas from Class Wells) was used

as Irrigation Gas. But most Class Wells (160 of 190) sent no gas for use as House or 

Irrigation Gas. Oxy used some gas from an unknown number of Class Wells as Field Gas 

to power its pumps and compressors.

Oxy sent the rest of the gas drilled from Class Wells for processing at the Jayhawk 

Plant under a contract with Amoco Production Company, the Plant's owner. Cooper's 

class definition includes only the gas from Class Wells sent for processing at the Plant 

(Class Gas); it excludes any raw gas from Class Wells used as House, Irrigation, or Field 

Gas. 
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At the Plant, Amoco extracted three individual components from raw Class Gas: 

Natural Gas Liquids (NGLs), Crude Helium, and Residue Gas. Amoco charged an inkind processing fee for its services: it retained 25% of NGLs and 50% of Crude Helium 

extracted from Class Gas. It also charged a processing fee for Residue Gas. Then Amoco 

delivered the three extracted components, minus the amount retained as a processing fee,

back to Oxy at the Plant. So Oxy received 100% of Residue Gas, 75% of NGLs, and 50% 

Crude Helium.

After processing, Oxy sold the components in the interstate market. Those sales 

had to occur after processing—until then, raw gas doesn't meet the minimum-quality 

standards set by the Federal Energy Regulatory Commission (FERC) for transporting gas 

on interstate pipelines. Oxy sold Residue Gas to its affiliate entity Occidental Energy 

Marketing, Inc. Occidental Energy paid Oxy the Southern Star Index Price—an 

established interstate-pipeline price based on a survey of transactions over a given period. 

Then Occidental Energy resold Residue Gas to third-parties. Occidental Energy also 

marketed NGLs for Oxy, selling the product to third-parties and passing on proceeds to 

Oxy. Oxy had a similar arrangement with Amoco for Crude Helium—Amoco marketed 

the product and passed on proceeds it received from buyers to Oxy. 

The royalty clauses

We've focused so far on the production process, tracing Class Gas from the well 

where Oxy extracted it to the interstate market where Oxy sold it. But to understand 

Cooper's claims, it would help to understand how Oxy paid landowners under Class 

Leases. 

Like all natural-gas leases, Class Leases require Oxy to pay royalties. Royalties

are paid monthly from the gas company to a landowner (the lessor) when land burdened 
7

by a lease produces gas. Cooper and Oxy dispute the proper method of calculating 

royalty under Class Leases. Oxy points to three types of royalty clauses recognized in 

Kansas: proceeds, market value, and Waechter. Under proceeds leases, the gas company 

pays royalty based on a percent of the actual money it receives from selling the gas. But 

with market-value leases, Oxy says the gas company pays based on the price a willing 

buyer would pay a willing seller in a free market. Waecther leases—named after the lease 

type in Waechter v. Amoco Production Co., 217 Kan. 489, 537 P.2d 228 (1975)—

combine aspects of proceeds and market-value leases, with payment depending on where 

the gas was sold. 

In the district court, both parties submitted a chart categorizing Class Leases by 

their royalty clauses. Both charts categorize Class Leases into 14 forms. Oxy's chart also 

sorts the leases into the three types we just mentioned. By Oxy's count, Cooper's class

includes 114 Waechter leases, 104 market-value leases, and 27 proceeds leases. Oxy's 

chart also classifies each lease form by the volume of gas on which Oxy says it had to 

pay royalty. Cooper disputes these classifications. 

The class action

On February 16, 2017, Cooper filed a class-action petition alleging that Oxy had 

underpaid royalties on Class Gas from July 1, 2007, to April 30, 2014 (Class Period). 

Oxy did so, the petition claimed, by deducting several processing expenses from 

royalties. Cooper said that those deductions violated Oxy's duties under Class Leases and 

entitled class members to recovery of unpaid royalties. 

Cooper sought to recover expenses from four deductions. First, Cooper alleged 

that Oxy deducted processing fees charged by Amoco for Residue Gas. Second, Cooper 

claimed that Oxy didn't pay royalty on the full volume of NGLs and Crude Helium 

recovered from Class Wells. In other words, Cooper said that Oxy didn't pay any royalty 
8

on the 25% NGLs and 50% Crude Helium retained by Amoco. Third, Cooper said Oxy 

paid royalty for Residue Gas on the Index Price rather than on the price Occidental 

Energy received from third parties when it resold the Gas. According to Cooper,

Occidental Energy's resale price was usually higher than the Index Price. 

Last, Cooper sought to recover interest on Conservation Fees deducted from 

royalty. Oxy pays Conservation Fees to the Kansas Corporation Commission and had 

been deducting them from royalty. It repaid those Conservation Fees to class members 

after our Supreme Court held that gas companies couldn't deduct them from royalty. But 

Oxy paid no interest on the repaid Conservation Fees. Cooper said that Oxy should have 

to pay interest on repaid Conservation Fees.

When Cooper moved to certify these claims as a class action, Oxy objected. And 

Oxy moved to strike the testimony of Cooper's expert witness. Cooper filed a reply brief 

supporting its certification motion and moved for partial summary judgment on several 

issues Oxy raises in this appeal. Oxy hadn't responded to Cooper's summary-judgment 

motion before the district court certified the class, so the district court hasn't yet ruled on 

it and that motion is not before us on appeal.

The certification order

In a 24-page order, the district court granted Cooper's motion and certified the 

class. The district court identified the statutory requirements for certification and

discussed each separately. See K.S.A. 2018 Supp. 60-223(a), (b)(3). It devoted 11 pages 

to the commonality requirement, identifying several common questions supporting 

certification:

 Oxy's legal duties under Class Leases, including the duty to market;
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 Whether Oxy breached the duty to market by deducting processing costs 

from royalty;

 Whether Oxy breached the mutual-benefit or best-available-price rule by 

paying royalty for Residue Gas on the Index Price rather than Occidental 

Energy's resale price; and 

 The damages calculation.

The court rejected Oxy's commonality arguments. Oxy had argued that because 

some gas from Class Wells had been used for House, Irrigation, and Field Gas, some 

Class Gas may have been marketable at the well. So determining when Class Gas was 

marketable, according to Oxy, presented individual questions that required a well-by-well 

analysis. Oxy had also argued that Hydrogen Sulfide (H2S) in some Class Wells may 

have made Class Gas unmarketable at the well. The district court considered Oxy's 

marketability arguments and found that they didn't preclude a commonality finding. 

Having found that Oxy met the prerequisites for certification under K.S.A. 60-

223(a), the court next addressed the predominance requirement of K.S.A. 60-223(b)(3).

Oxy had argued that its statute-of-limitations defense raised individual issues that would 

predominate over questions common to all class members. The court found that it need 

not consider evidence relevant to affirmative defenses like the statute of limitations when 

deciding predominance. Yet the court still considered Oxy's defense, concluding that 

predominance remained intact because the parties could litigate Oxy's defense classwide. 

Because the court found that Cooper's petition met the statutory requirements, it certified 

the Class. 

Oxy appealed the district court's certification decision to our court.
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ANALYSIS

When a party challenges a district court's decision to certify a class action, as Oxy 

does here, we begin our analysis with the class-action statute, K.S.A. 2019 Supp. 60-223.

That statute gives the district court substantial discretion in deciding whether certification 

is appropriate. If the trial judge considers the relevant factors listed in the statute, then we 

review its decision for abuse of discretion. It abuses its discretion if its decision is based 

on legal or factual error, or if its decision is arbitrary or unreasonable. Factual findings 

must be supported by substantial evidence; we review legal questions independently, with 

no required deference to the district court. Coulter, 296 Kan. at 351-52.

To certify a class action, the district court must make two findings. First, it must 

find that the class meets four prerequisite requirements: (1) numerosity, (2) commonality, 

(3) typicality, and (4) adequacy of representation. K.S.A. 2019 Supp. 60-223(a). Second, 

it must find that one of the circumstances in K.S.A. 2019 Supp. 60-223(b) exists; the 

district court found that common questions would predominate over individual ones 

under K.S.A. 2019 Supp. 60-223(b)(3). Oxy raises four issues with the district court's 

certification decision that each relate to one of the perquisite requirements in subsection 

(a) or the circumstances in subsection (b). We will address each of Oxy's four arguments. 

I. The District Court's Certification Decision Was Not Based on a Misreading of Fawcett. 

Oxy first argues that the district court certified Cooper's class based on a 

misinterpretation of our Supreme Court's opinion in Fawcett. That case dealt with the 

meaning of a legal doctrine called the marketable-condition rule. To better understand 

Oxy's position, we briefly discuss the general principles of that rule. 

Under Kansas law, all gas leases impose an implied duty on the gas company to 

market any gas produced from a well. Unless disclaimed by express language, that means

the gas company must market its product at reasonable terms within a reasonable time 
11

following production. Fawcett, 302 Kan. at 351. A corollary of that duty is the 

marketable-condition rule, which requires gas companies to make gas marketable at their 

own expense (meaning they can't deduct those expenses from royalty). 302 Kan. at 352, 

361. But when is gas considered in a "marketable condition" so that a company can start 

deducting expenses? 

Oxy's first argument is rooted in the parties' disagreement on the answer to that 

question. Oxy says the district court adopted Cooper's view that, under Fawcett, Class 

Gas was marketable only after it was sold in good faith. That view misreads Fawcett, 

Oxy argues, because Fawcett didn't alter the long-held rule in Kansas that gas can be 

marketable at the well before it is sold. And if that's the case, then certification may have 

been improper because the district court would have to analyze each Class Well one-byone to see if the gas from that well was marketable based on several factors. Put another 

way, it would have to conduct the kinds of individualized inquiries that preclude a 

commonality finding. So Oxy asks us to instruct the district court to consider whether 

certification is appropriate under Oxy's reading of Fawcett. We turn next to Fawcett so 

we can resolve the parties' divergent views on its holding. 

Like our case, Fawcett involved a class action for royalty underpayment. But 

unlike this case, the gas company in Fawcett sold the gas to third parties at the well. The 

third parties paid the gas company a price that deducted processing costs, then the gas 

company paid royalty based on that price rather than on the gross value of the gas without 

processing costs subtracted. The plaintiffs argued that paying royalty with processing 

costs deducted violated the marketable-condition rule. The gas was not marketable, 

argued the plaintiffs, until it entered interstate pipelines after processing. So the gas 

company should have incurred all costs necessary to prepare the gas for interstate 

transmission, including the deducted processing costs. 302 Kan. at 351-52. 
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The Kansas Supreme Court disagreed. The court acknowledged that when gas 

becomes marketable remains an "open question" in Kansas. 302 Kan. at 363-64. But 

whatever marketable means, gas is always marketable when it has been sold. The first 

sale of the gas at issue occurred at the well. When that sale occurred, the gas must have 

been in a marketable condition because it had been marketed. 302 Kan. at 364. "[T]he 

duty to make gas marketable is satisfied," the court said, "when the operator delivers the 

gas to the purchaser in a condition acceptable to the purchaser in a good faith 

transaction." 302 Kan. at 365. So the gas company in Fawcett could deduct the 

processing costs without violating the marketable-condition rule because it had incurred 

those costs after the point at which the gas became marketable—the first sale at the well.

302 Kan. at 365-66.

Now let's return to the parties' dispute about Fawcett's holding. Recall that Cooper 

reads Fawcett as holding that gas cannot be in a marketable condition until it is sold in a 

good-faith transaction. Under that view, Oxy violated the duty to market when it 

deducted pre-sale expenses from royalty. But Fawcett didn't say that gas is marketable 

only when it is sold; it said that a good-faith sale satisfies the marketable-condition rule 

because gas that has been marketed is always marketable. In other words, a sale is

sufficient but not necessary for gas to be in a marketable condition. See 302 Kan. at 365. 

If the court had intended for sales to be the only way gas could become marketable, then 

there would have been no point in noting that the meaning of marketability "remains an 

open question." 302 Kan. at 363. Cooper's marketable-means-sale reading of Fawcett

reaches too far. 

Oxy's reading of Fawcett is more nuanced than Cooper's but it fares no better. As 

we noted earlier, Oxy reads Fawcett as confirming a long-standing rule that gas sold 

away from the well may be marketable at the well pre-sale. If so, then Class Gas may 

have been marketable at the well before processing, allowing Oxy to deduct processing 

costs from royalty because it incurred those expenses pre-sale. Oxy cites two Kansas 
13

Supreme Court cases that it says support this view: Sternberger v. Marathon Oil Co., 257

Kan. 315, 894 P.2d 788 (1995), and Coulter, 296 Kan. 336.

Unlike in Fawcett, there was not a market for the gas in Sternberger at the well. 

The gas company couldn't persuade a buyer to build a pipeline that connected to the 

company's wells. So the company built its own pipeline to transport the raw gas from the 

wells to a larger pipeline for sale. It deducted a portion of the pipeline construction cost 

from royalties. A class of royalty owners sued the company to recover those costs. 257 

Kan. at 318-20. 

The Sternberger court held that the gas company could deduct the pipelineconstruction costs from royalties. The court summarized Kansas law on the marketablecondition rule: "Once a marketable product is obtained, reasonable costs incurred to 

transport or enhance the value of the marketable gas may be charged against nonworking 

interest owners." 257 Kan. at 331. The royalty owners in Sternberger offered no evidence 

that the gas was not already in a marketable condition at the well in its raw form. The 

pipeline didn't alter the physical quality of the gas—it merely moved the gas from the 

well to a larger pipeline. The gas was already marketable at the well but there was no 

buyer there, so the gas could be sold only if transported elsewhere. Thus, the gas 

company didn't violate the marketable-condition rule by deducting some of the pipelineconstruction costs from royalty because those deductions occurred after the gas was 

already marketable. 257 Kan. at 331-32.

Oxy reads Sternberger as holding that gas can be marketable at the well even if no 

market exists there. If so, and if Fawcett didn't overturn Sternberger, then Class Gas 

could have been marketable pre-sale at the well. But even if gas can be marketable at the 

well, how does Oxy know that the Class Gas here was marketable at the well? Oxy says 

the answer lies in Coulter.
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In Coulter, the defendant argued that some of the gas in that case was in a 

marketable condition at the well. Our Supreme Court addressed that argument in dicta—

the court was deciding whether a district court erred in affirming a class-action 

settlement, not the meaning of marketability. The court noted that some gas was used as 

House Gas, which suggested that "gas at the well site [was] in a marketable condition for 

household use." 296 Kan. at 365. And some gas was used as Irrigation Gas, which 

showed that "the gas [was] in marketable condition for use in irrigation systems before it 

[was] in a condition to enter the interstate transmission pipeline." 296 Kan. at 365. These 

issues presented "unresolved factual and legal questions" about the marketability of the 

gas. 296 Kan. at 365. Oxy makes a similar point about determining the marketability of 

Class Gas. 

Oxy observes that Class Gas, like the gas in Coulter, may have been marketable at 

the well. A small amount of gas from Class Wells was never processed—it went straight 

from the well for use as House, Irrigation, and Field Gas. Oxy says some Class Gas may 

have been usable at the well for those purposes too, even though Cooper excluded gas 

from Class Wells used for those purposes from the class definition. Oxy contends that 

determining whether any Class Gas was usable at the well should preclude certification

because it would require a well-by-well analysis. 

Taken to its logical conclusion, Oxy's interpretation of Coulter, Sternberger, and 

Fawcett would substantially erode the marketable-condition rule. Oxy argues that 

because some gas from Class Wells was usable at the well for House, Irrigation, and 

Field Gas, all Class Gas could have been usable at the well for those purposes. Of course, 

no Class Gas was used for those purposes—Oxy sent all Class Gas to the Plant for 

processing and sale in the interstate market. So Oxy must be arguing, as it admitted at 

oral argument, that all gas from a well is marketable the moment any gas from that well is

usable for some purpose, even if the gas will not be used for that purpose. Our Supreme 

Court rejected that view of marketability over a century ago because all gas is usable for 
15

some purpose the moment it leaves the ground. See Ely v. Wichita Natural Gas Co., 99 

Kan. 236, 246-47, 161 P. 649, 652-53 (1916).

If that were all it took for gas to be considered marketable, then gas companies 

could deduct every expense incurred after the gas leaves the ground on the theory that 

some gas is already usable for some purpose. Such a rule would hollow out the 

marketable-condition rule and render it meaningless. Oxy's reading of Fawcett, like 

Cooper's, reaches too far.

Neither Oxy nor Cooper offers a workable theory of marketability after Fawcett. 

Oxy says Class Gas was in a marketable condition if it was usable at the well for any 

purpose. But that approach would make all gas marketable at the well because all gas is 

usable in its raw form for some purpose. Cooper equates marketability with sales, an

approach at odds with Fawcett. Fawcett held that a sale satisfies the duty to market, but it 

did not hold that a sale was the only way to satisfy that duty. Fortunately, there's a better 

way to read Fawcett.

Through their conduct, the parties in Fawcett had defined a market at the well, 

where the gas company had arranged for a buyer to buy the gas. When those sales 

occurred, the gas may not have been in a condition suitable to other buyers in other 

markets downstream. But the gas was in a condition acceptable to a buyer in the only 

market that mattered—the one created by the parties through their actions. The buyer had 

some use for the gas and it was evidently already in a condition suitable for that use at the 

well. 302 Kan. at 364-65. Fawcett establishes a simple principle: when parties define a 

market for gas through their conduct, that gas is marketable when it is in a condition 

acceptable for that intended market. 

The concept of marketability is tied to the market for the gas. As we noted, the 

quantity of gas available in the Hugoton Field vastly exceeds any market for the use of 
16

unprocessed gas for House, Irrigation, or Field Gas. Cooper has defined Class Gas to 

include only the gas intended for the interstate market; the small quantities used for 

House, Irrigation, or Field Gas are excluded. When the parties have agreed that the gas 

will be sold in the interstate market, the gas company cannot deduct expenses required to 

make the gas marketable for that interstate market.

That principle tracks with Sternberger and Coulter too. The Sternberger gas was 

of a quality capable of being transported in interstate pipelines without processing—it

simply had to be moved from one place to another. So the gas company could deduct the 

costs of building a transportation pipeline to bring the marketable gas to the market

intended by the parties. 257 Kan. at 330-32. And in Coulter, gas used near the well as 

House and Irrigation Gas was marketable for those purposes in those markets. 296 Kan. 

at 365. Those uses, like the well sales in Fawcett, were conclusive evidence of

marketability. 

When applied here, the market-driven definition of marketability easily resolves 

the parties' claims. Oxy didn't sell any Class Gas at the well; it sold all Class Gas 

downstream in the interstate market. Until Class Gas was processed, it fell below FERC's 

minimum-quality standards for transporting gas in interstate pipelines. So Class Gas 

wasn't in a condition suitable for its intended market until Amoco delivered the processed 

components (now up to FERC's standards) back to Oxy at the Plant. All royalty 

deductions from costs incurred before that point violated the marketable-condition rule; 

deductions after that point did not.

Under this view, the district court didn't need to consider Oxy's list of general 

marketability factors because none could have affected the marketability of Class Gas. 

Take Oxy's claim that the district court should have considered whether any Class Gas 

was usable at the well for House, Irrigation, or Field Gas. Those factors may affect 

marketability in other cases, but they don't do so in our case when the parties defined the 
17

market for Class Gas. Oxy sent all Class Gas to the Plant for processing and sale in the 

interstate market; no Class Gas was intended for use at the well. That Class Gas may 

have been in a suitable condition at the well for the House, Irrigation, and Field Gas 

markets doesn't affect the only relevant inquiry: when was Class Gas suitable for the 

interstate market where Oxy intended to sell it?

Consider Oxy's argument about HS2 content. A high H2S content makes gas 

unmarketable, notes Oxy, so some Class Gas may have been unmarketable if any Class 

Wells had a high H2S content. Again, this doesn't matter because all Class Gas was 

unmarketable until it was in a condition suitable for the market intended by the parties 

(until it was processed). We don't need to know what the H2S content of gas from 

individual Class Wells was because all Class Gas was unmarketable at the well regardless 

of H2S content; the dispositive inquiry is the intended market for the gas and that inquiry 

isn't influenced by H2S content. Even if H2S were relevant, its effect on marketability 

would present a common question because both parties agree that Oxy removed it after 

gathering Class Gas into a single stream on the way to the Plant for processing. As with 

the other factors Oxy says affect marketability, we need not consider H2S content to 

determine when Class Gas was marketable for interstate sales, the intended market here. 

Now that we've established a workable definition of marketability, we can apply it 

to Cooper's three claims. The first two deductions occurred before the Class Gas was 

marketable. First, Cooper alleges that Oxy deducted a processing fee for Residue Gas.

Oxy incurred that expense before processing. It was a cost incurred to get Class Gas in a 

condition suitable for interstate sales. So Oxy could not deduct it. Second, Cooper claims 

that Oxy didn't pay royalty on the 25% NGLs and 50% Crude Helium retained by Amoco 

as an in-kind processing fee. Like the first deduction, this was a processing expense Oxy 

incurred to put Class Gas in a condition suitable for interstate sales. So Cooper may also 

state a claim based on Oxy not paying royalty on the full volume of NGLs and Crude 

Helium. 
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Cooper's last claim is a different story. That claim says that Oxy violated the 

marketable-condition rule by paying royalty for Residue Gas on the Index Price rather 

than on the Occidental Energy's resale price. Residue Gas had been processed when these 

sales occurred, so the gas was already in a marketable condition. Oxy didn't violate the 

marketable-condition rule by paying royalty on the Index Price.

 

To be clear, Oxy may have violated other duties by paying the Index Price. 

Cooper's class petition alleged that Oxy's Index Price scheme violated two duties other 

than the marketable-condition rule: the duty of good faith and the duty to obtain the best 

available price. Those duties are distinct from the marketable-condition rule. Fawcett, 

302 Kan. at 361, 365-66; see McArthur, Mineral Royalties, Deductions, and Fawcett v. 

Opik: Continuity and Change in the Revised-But-Still-Standing Kansas MarketableProduct Rule, 64 U. Kan. L. Rev. 63, 81-85 & n.80 (2015). Our conclusion that Oxy did 

not violate the marketable-condition rule by paying royalty on the Index Price says 

nothing about whether that conduct violated these other duties. Cooper's Index Price 

claims can proceed based on those other duties but not based on the marketable-condition 

rule.

Let's review what we've established so far. Under Fawcett, Class Gas wasn't

marketable until it was in a condition suitable for its intended market. All Class Gas was 

bound for the interstate market and wasn't of a quality suitable for that market until it was 

processed. So Class Gas was marketable after processing. Two of Cooper's marketablecondition claims allege that Oxy deducted pre-marketability expenses from royalty. 

Those claims fit Fawcett's definition of marketability and can proceed. But Cooper's third 

claim—that Oxy paid royalty for Residue Gas on the Index Price—is based on a postprocessing deduction after the gas was already marketable. Although this means Cooper 

doesn't have a claim under the marketable-condition rule for that deduction, Cooper may 

still state claims that paying the Index Price violated other duties in Class Leases. 
19

Before moving on, we need to address one more point on the Fawcett issue. At 

oral argument, Oxy emphasized an unpublished federal district court opinion that 

discusses Fawcett. See Hitch Enterprises, Inc. v. Oxy USA Inc., No. 18-1030-EFM-KGG, 

2019 WL 3202257 (D. Kan. 2019) (unpublished opinion), rev. denied No. 19-609 (10th 

Cir. Feb. 10, 2020). We aren't bound by that court's interpretation of Kansas natural-gas 

law, but we are all trying to get it right. See Kansas Public Employees Retirement System

v. Reimer & Koger Assocs., Inc., 262 Kan. 635, 669-70, 941 P.2d 1321 (1997). With that 

in mind, let's examine Hitch.

Hitch involved the same facts as our case. The plaintiffs sought certification for 

royalty underpayment based on deductions they alleged were made before the gas was 

marketable, and the parties disputed the meaning of marketability based on Fawcett. The 

plaintiffs offered the marketable-means-sale reading of Fawcett while Oxy, who was also 

the defendant in Hitch, argued that Fawcett didn't alter the long-held rule in Kansas that 

gas can be marketable at the well. 2019 WL 3202257, at *4. 

We agree with much of Judge Eric Melgren's analysis in Hitch. Judge Melgren 

read Fawcett (as we do) as holding that a good-faith sale is sufficient but not necessary to 

satisfy the marketable-condition rule. 2019 WL 3202257, at *5. He also concluded that 

Fawcett left Sternberger's holding—that gas may be marketable at the well before a 

sale—untouched. 2019 WL 3202257, at *6. We agree with that too. 

But our agreement ends there. Judge Melgren denied certification of the plaintiffs'

marketable-condition claims based on Coulter—he considered House and Irrigation Gas 

use from some wells as evidence of marketability at the well even though the class 

definition excluded that gas. 2019 WL 3202257, at *8. Unlike Judge Melgren, we are 

unconvinced that the usability of a small amount of gas at the well as House or Irrigation 

Gas affects the marketability of the vastly greater share of the gas that is destined for the 
20

interstate market. We've already discussed the problem with accepting that argument—all 

gas is usable at the well for some purpose. We decline to follow Judge Melgren's analysis 

because doing so would undermine the marketable-condition rule.

II. The District Court Did Not Abuse its Discretion When it Found That Cooper's Class 

Petition Raised Questions of Law and Fact Common to All Class Members.

Oxy next objects to the district court's commonality finding. Commonality is one 

of the four requirements that must exist before a trial judge can certify a class action—the 

plaintiffs' petition must present questions of law or fact common to all class members. 

K.S.A. 2019 Supp. 60-223(a)(2). That means the proposed class members must state 

claims that depend on a "common contention that is capable of class-wide resolution, 

meaning that determination of its validity will resolve an issue that is central to the 

validity of each of the claims with one answer." Critchfield Physical Therapy v. The 

Taranto Group, Inc., 293 Kan. 285, 295, 263 P.3d 767 (2011). Put differently, 

commonality exists if it's "possible for the litigation to generate answers in common for 

the proposed class to questions raised in common by the class." 293 Kan. at 297.

Oxy raises three issues with the district court's commonality findings. First, Oxy 

argues that variations in the language in Class Leases preclude a commonality finding. 

Second, Oxy contends that resolving the factual issues in the case will require Cooper to 

present individualized evidence. Third, Oxy says that whether it owes interest on repaid 

Conservation Fees is an individualized question. None of these arguments preclude a 

commonality finding.

Disclaimer language in Class Leases doesn't destroy commonality.

Oxy's first commonality argument is that whether the duty to market exists in 

Class Leases presents individual questions because language in some leases may disclaim 

that duty. 
21

All gas leases in Kansas contain the implied duty to market. Fawcett, 302 Kan. at 

366. A gas company may only disclaim that duty with clear and express language to that 

effect. Farrar v. Mobil Oil Corp., 43 Kan. App. 2d 871, 887-88, 234 P.3d 19 (2010). The 

express language must authorize the specific deduction taken. See Gilmore v. Superior 

Oil Co., 192 Kan. 388, 392-93, 388 P.2d 602 (1964). 

Oxy doesn't dispute that the duty to market exists in all Class Leases. It instead 

argues that some Class Leases contain language disclaiming that duty. Because the 

royalty-clause language in Class Leases varies from one lease form to another, Oxy 

contends that interpreting the leases to determine whether any disclaim the duty to market 

raises individual questions that should preclude a commonality finding. 

The district court rejected this argument. To disclaim the duty, the court said Oxy 

needed to show clear and express language authorizing a specific deduction. The court 

cited an example of a lease Cooper provided that explicitly disclaimed the marketing 

duty. That lease waived the duty "by using the word 'less' or 'minus' followed by specific 

naming of the costs that can be deducted." No Class Lease contained such specific 

language, so the court found that none disclaimed the duty to market. Thus, the court 

rejected Oxy's claim that whether any leases contained disclaimer language presented 

individual questions.

On appeal, Oxy focuses on two aspects of the lease language that purportedly 

disclaim the duty to market: volume and pricing. As to volume, Oxy claims that some 

individual leases contain language allowing Oxy to pay royalty on less than the full 

volume of gas produced from a well. Oxy relies on phrases like "gas sold," "gas 

produced," and "gas marketed" in the leases. Those phrases, Oxy argues, could allow 

royalty payments on less than the full volume of gas. Oxy also cites variations in lease 

types (proceeds, market value, and Waechter) as having that same effect. Whatever the 
22

language, Oxy's point is the same: interpreting Class Leases to determine whether any 

disclaim the duty to market presents individualized questions that destroy commonality. 

There are three problems with this argument.

First, any volumetric language disclaiming the duty to market would apply only to 

Cooper's allegation about retainage fees. That allegation says that Oxy failed to pay 

royalty on the 25% NGLs and 50% Crude Helium retained by Amoco as an in-kind 

processing fee. Cooper's other allegations don't turn on the volume of gas on which Oxy 

paid royalty. So even if Oxy is correct that individual leases may have allowed Oxy to 

pay royalty on less than the full volume of gas produced from Class Wells, that 

conclusion would not affect commonality on Cooper's remaining claims.

Second, even if the volume-language issue presented individual questions, it

wouldn't preclude class certification. Oxy frames this issue as an objection to the district 

court's commonality finding, but it doesn't argue that the individual questions posed by 

volume language in leases would predominate over common questions. As we'll discuss 

later, Oxy's only predominance argument relates to its statute-of-limitations defense. So 

even if volume language in leases generates individual questions, the district court didn't 

abuse its discretion because Oxy has not shown that those questions would predominate. 

Third, individual questions wouldn't arise from Oxy's volume argument because 

the district court correctly found that no Class Leases disclaim the duty to market. We 

exercise unlimited review over that finding because interpreting a gas lease is a legal 

question. Fawcett, 302 Kan. at 359. As a matter of Kansas law, waiving the duty to 

market requires express language authorizing a specific deduction. Farrar, 43 Kan. App. 

2d at 887-88. And as the district court noted, no Class Lease mentions Amoco's in-kind 

processing fee or authorizes Oxy to subtract that fee from royalty. So the district court 

properly rejected Oxy's lease-language argument about gas volume. 
23

Oxy's other disclaimer argument is based on pricing language in Class Leases.

Oxy contends that the district court cannot decide whether paying royalty for Residue 

Gas on the Index Price violated lease duties classwide because it applies to only proceeds 

leases. Oxy appears to be arguing that paying royalty on the Index Price could never 

violate the duty to market under Waechter and market-value leases. In other words, Oxy 

says that the pricing allegation isn't a common question because it only applies to 

proceeds leases. 

Oxy cites no authority directly supporting this argument. The district court noted 

that it wasn't aware of any Kansas cases interpreting proceeds and market-value leases 

differently, as Oxy asked it to. On appeal, Oxy cites cases purporting to describe the 

difference between proceeds and market-value leases. But those cases don't say that 

market-value or Waechter leases authorize payment on the Index Price or that paying that 

price could never violate the duty to market for those lease types. 

The pricing argument has other problems too. Oxy frames it as a commonality 

issue, not a predominance issue. So even if we found that individual questions arose 

based on the differences between proceeds leases and other lease types, Oxy has not 

argued that those questions would predominate over common ones. And because the 

Index Price claim is only one of Cooper's three claims, success for Oxy on this argument 

wouldn't affect Cooper's remaining claims—it would simply mean that the Index Price 

claim presents individual questions that do not predominate over common ones. Nor 

would it defeat Cooper's Index Price claim because it at best relates to the duty to market. 

Oxy never argued that the lease-type differences somehow disclaimed the other duties 

Cooper alleged were violated by paying the Index Price (the duty of good faith and the 

duty to obtain the best price available). 

And both the volume and pricing arguments are common questions even if the 

district court abused its discretion in rejecting them. Again, the interpretation of gas 
24

leases is a question of law. Fawcett, 302 Kan. at 359. Whether any leases disclaim the 

duty to market is a question that the district court can answer classwide. On the volume 

argument, Oxy says some leases contain language allowing payment on less than the full 

volume of gas produced from Class Wells. The district court can interpret that language 

and decide classwide whether that's the case. On the pricing argument, the court can 

make a single finding on whether market value and Waechter leases allow payment on 

the Index Price. So neither of Oxy's language arguments preclude a commonality finding.

Cooper's claims can be litigated classwide without individualized evidence.

Oxy's second commonality argument is that Cooper's claims will require 

individualized evidence from each class member. Oxy relies on the United States 

Supreme Court's opinion in Tyson Foods, Inc. v. Bouaphakeo, 577 U.S. ___, 136 S. Ct. 

1036, 194 L. Ed. 2d 124 (2016), for this argument. 

One issue in Tyson centered on the predominance requirement in Rule 23 of the 

Federal Rules of Civil Procedure. Under Rule 23(b)(3), federal district courts must find 

that "questions of law or fact common to class members predominate over any questions 

affecting only individual members." When interpreting that provision, the Court

described individual questions as those requiring class members to "'present evidence that 

varies from member to member.'" 136 S. Ct. at 1045. But with common questions, "'the 

same evidence will suffice for each member to make a prima facie showing [or] the issue 

is susceptible to generalized, class-wide proof.'" 136 S. Ct. at 1045. 

The Tyson Court applied those definitions to a class action brought by employees 

at a food-processing plant alleging violations of the Fair Labor Standards Act of 1938. 

They claimed that Tyson didn't pay them overtime they had a right to receive under the 

Act for time they spent taking protective gear on and off. The parties agreed that whether 

that time was compensable work under the Act was a common question. But there were 
25

also questions affecting individual employees. Because the Act only covers employees 

who work more than 40 hours a week, each employee had to prove that they met the 

weekly hours requirement. Doing so proved difficult, however, because Tyson didn't 

keep records of time spent taking the protective gear on and off. Tyson argued that each 

individual employee would have to prove the amount of weekly time spent putting on and 

taking off the gear. According to Tyson, that inquiry would predominate over questions 

common to the class. 

Without employer records, the employees relied on statistical evidence to show 

that they met the hours requirements. They provided a study estimating the average time 

an employee spent taking the protective gear on and off. The employees added that 

estimate to each class member's hours to determine whether class members met the 40-

hours threshold. Because the employees' study provided a way to determine hours 

classwide, the Court held that Rule 23's predominance requirement was satisfied. 136 S. 

Ct. at 1048-49.

Oxy says that Cooper's claims don't meet Tyson's definition of commonality. As 

Oxy sees it, Tyson focuses the individual-versus-common question inquiry on whether all 

class members will present identical evidence. For Oxy, the factual issues in Cooper's 

petition present individual questions because individual records exist for each Class Well. 

If each class member sued individually, Oxy says they would have to rely on evidence 

specific to their individual wells. And even if Cooper can present expert testimony about 

all class members, the expert would have to analyze each individual lease and evidence 

particular to each individual well. Thus, Oxy says Tyson supports its opposition to 

certification.

We disagree because Cooper's claims fit Tyson's definition of commonality. To 

establish that Oxy breached duties in Class Leases, Cooper will present the same 

evidence for each class member because the claims center on Oxy's conduct. Cooper will 
26

rely on Oxy's documents showing the expenses it incurred putting Class Gas in a 

marketable condition, the royalty deductions it took, and the agreements it entered with 

Occidental Energy and Amoco. None of that information will vary for any individual 

class member—each member would put on the same evidence if they brought their 

claims individually.

Cooper's three allegations highlight this point. Cooper first alleges that Oxy's 

affiliate-pricing scheme violates implied lease duties. To prove that claim, Cooper relies 

on Oxy's marketing agreement with Occidental Energy and records comparing the resale

price with the Index Price. Oxy doesn't dispute that it paid royalty for Residue Gas to all 

class members on the Index Price, so litigating the affiliate-price allegation will not 

require individualized evidence. 

Nor will litigating Cooper's second allegation. Cooper says Oxy didn't pay royalty

on the 25% of NGLs and 50% of Crude Helium retained by Amoco as an in-kind 

processing fee. That fee was established in Oxy's contract with Amoco and confirmed by 

Amoco's plant statements. Cooper's expert obtained the list of Class Wells subject to that 

fee by examining Oxy's payment data. Without relying on evidence from any individual 

class member, Cooper can show that Oxy processed all Class Gas at the Plant and that all 

gas Oxy sent to the Plant was subject to the in-kind fee. Like the first allegation, Cooper 

can present classwide evidence that Oxy didn't pay royalty on the gas retained by Amoco. 

The same goes for Cooper's third allegation. That allegation is about processing 

fees for Residue Gas and proving it will require Cooper to show that Oxy deducted those 

fees from all Class Gas. Cooper can do so with Oxy's payment data. It needs no evidence 

from individual class members. For all three allegations, then, common evidence can be 

presented for all class members—expert testimony and documents from Oxy and thirdparties. 
27

Oxy also argues that class members will have to present individual evidence to 

prove damages. But Cooper presented enough evidence for the district court to find that 

Cooper could calculate damages classwide. Cooper's expert showed the ability to do so 

using Oxy's payment data. With that data, Cooper's expert calculated classwide damages 

for each month during the Class Period. Other courts have upheld similar damages 

calculations when challenged at the certification stage. See Naylor Farms, Inc. v. 

Chaparral Energy, LLC, 923 F.3d 779, 798 (10th Cir. 2019). We follow their lead and do 

the same here. The district court did not err in finding that Cooper's claims were capable 

of classwide resolution without individual evidence from class members.

The dispute over interest on repaid Conservation Fees is a common question.

Oxy's final commonality argument is that the district court abused its discretion 

when it found that the parties' dispute over interest on repaid Conservation Fees was a 

common question affecting all class members. The Kansas Corporation Commission 

assesses a Conservation Fee on first purchasers of gas produced in Kansas. See K.S.A. 

2018 Supp. 55-176; K.A.R. 82-3-307(a). The Kansas Supreme Court held in 2011 that 

gas companies could not deduct Conservation Fees from royalty payments. Hockett v. 

The Trees Oil Co., 292 Kan. 213, Syl. ¶¶ 4-5, 251 P.3d 65 (2011). After Hockett, Oxy 

refunded class members Fees it had been deducting from royalties. But Oxy didn't pay 

any interest on refunded Fees. 

The parties dispute what statute applies to determine whether and at what rate 

class members should receive interest on refunded Conservation Fees. Cooper maintains 

that the general interest-rate statute applies. Under that statute, Oxy would owe each class 

member 10% annual interest on repaid Fees. K.S.A. 16-201. Oxy counters that specific 

statutes involving interest on oil and gas payments should apply. K.S.A. 55-1614; K.S.A. 

55-1615. Under those statutes, interest does not accrue on "[e]xcluded payments"

(payments totaling less than $100 annually). K.S.A. 55-1614(i). If Oxy deducted less than 
28

$100 in Conservation Fees from a class member's royalty payments in a given year, then 

that plaintiff wouldn't be entitled to any interest on repaid Conservation Fees for that 

year. Oxy reasons that Cooper's Conservation Fee claim presents individual questions

because the district court would have to determine whether the excluded-payments 

exception applied to each class member by calculating the amount of annual 

Conservation Fees deducted from royalties during each year of the Class Period. 

Oxy cites two unpublished federal cases supporting its position. In both cases, 

Judge Melgren found that Oxy's statutes should apply because they were more specific.

See Hitch, 2019 WL 3202257, at *9-11; Roderick v. XTO Energy, Inc., No. 08-1330-

EFM-GEB, 2016 WL 4039641, at *10-12 (D. Kan. 2016) (unpublished opinion). 

We need not decide which statute applies. We agree with the district court that

whether Oxy owes interest on repaid Conservation Fees, and if so, how much, is a 

question common to all class members. The district court declined to answer that

question at the certification stage because the parties had not fully briefed it. Oxy will get 

the chance to argue its position after this appeal because Cooper has included the 

Conservation Fees issue in the pending summary-judgment motion. The district court can 

weigh in on the Conservation Fees issue when it decides that motion after the parties 

have developed their positions more fully. The district court did not err in its decision that 

the Conservation Fees issue presents a common question supporting class certification, 

and that's all we need to decide now. 

The district court can always reevaluate certification if it later finds that Oxy is 

right about the interest-rate statute that applies. If determining whether each class 

member received more than $100 in each class year presents individualized questions, 

then the district court can consider whether those questions predominate over common 

ones. If so, it could amend the certification order as needed. See K.S.A. 2019 Supp. 60-

223(c)(1)(C). Of course, if the district court finds that K.S.A. 16-201 applies, then no 
29

individual questions would arise because all class members would receive 10% annual 

interest on repaid Fees.

III. The District Court Did Not Abuse Its Discretion When It Found That Common 

Questions Predominate Over Issues Involving Oxy's Statute-of-Limitations Defense. 

Oxy next argues that its statute-of-limitations defense raises individual questions 

that predominate over common questions. 

For a class action certified under subsection (b)(3), as the district court did here, it 

must find that "questions of law or fact common to class members predominate over any 

questions affecting only individual members." K.S.A. 2019 Supp. 60-223(b)(3). 

Predominance is a more demanding standard than commonality. Farrar, 43 Kan. App. 2d 

at 875-76. It requires that "common questions must be more significant than individual 

ones, but it does not require that all issues in the suit have common answers and common 

evidence." O'Brien v. Leegin Creative Leather Prod., Inc., No. 108,988, 2014 WL 

1362657, at *10 (Kan. App. 2014) (unpublished opinion). Instead, predominance tests 

whether the class is "sufficiently cohesive to warrant adjudication by representation."

Farrar, 43 Kan. App. 2d at 875.

We first examine the district court's claim that it wasn't required to consider Oxy's 

statute-of-limitations defense when making a predominance finding. The district court 

found that when deciding predominance, it considers only evidence relevant to the 

plaintiff's prima facie case, not to affirmative defenses like statute of limitations. It cited 

several authorities supporting that view. It quoted Tyson's statement that a district court 

can certify a (b)(3) class action "'even though other important matters will have to be 

tried separately, such as . . . affirmative defenses peculiar to some individual class 

members.'" 136 S. Ct. at 1045. And it cited a treatise on class actions under Rule 23. 2 

Rubenstein, Newberg on Class Actions, § 4:57 (5th ed. 2012) ("Statute of limitations 
30

defenses—like damage calculations, affirmative defenses, and counterclaims—rarely 

defeat class certification.").

We disagree with the district court on this point. Under Kansas law, the district 

court was free to consider evidence relevant to Oxy's statute-of-limitations defense when 

evaluating predominance. Nothing in the text of K.S.A. 2019 Supp. 60-223(b)(3) 

precludes consideration of affirmative defenses when deciding predominance. And no 

Kansas court has ever interpreted that provision as barring consideration of affirmative 

defenses. Nor do the sources cited by the district court support such a requirement. Those 

sources simply say that affirmative defenses rarely defeat certification because any 

individual issues arising from them "can be resolved during the damage phase of the case 

and need not preclude certification of liability issues." 2 Rubenstein, Newberg on Class 

Actions, § 4:57 (5th ed. 2012). So the district court should have considered evidence 

about affirmative defenses when deciding predominance.

Actually, though, it did. Although it said it wasn't required to consider affirmative 

defenses, the district did consider whether Oxy's statute-of-limitations defense presented 

individual questions, and if so, whether those questions predominated over common ones. 

The court found that Oxy's defense was a common question because it could be resolved

classwide. We must determine whether that was an abuse of discretion; we begin by 

taking a closer look at Oxy's defense.

Oxy argues that the statute of limitations bars Cooper's claims. The limitations

period on those claims is five years. K.S.A. 60-511. Cooper states claims for royalty 

deductions taken from July 1, 2007, to April 30, 2014. Cooper didn't sue until 2017, so 

the statute of limitations may bar claims from 2007 to 2012. But Cooper can defeat that 

defense by proving equitable estoppel. In Oxy's view, proving equitable estoppel would 

predominate over any common questions because it would require individual evidence 

and testimony from each class member. 
31

Oxy cites four federal cases in support of this argument, but we do not find them 

persuasive.

The first case denied certification under Rule 23 because "[a]pplication of the 

statute of limitations and the discovery rule involve[d] the consideration of facts unique 

to each class member." Doll v. Chicago Title Ins. Co., 246 F.R.D. 683, 687 (D. Kan. 

2007). When the limitations period began to run in Doll turned on when class members 

discovered their claims. The discovery inquiry involved detailed fact-finding about 

whether and when each class member was on notice of the claims.

Unlike the unique and individualized proof required in Doll, Cooper has presented 

common classwide evidence on equitable estoppel. Cooper's expert alleges that Oxy's 

contracts with Occidental Energy and the Processor are "confidential documents [that]

royalty owners cannot access." From that evidence, Cooper alleges that no class member 

could have known that Oxy was deducting certain expenses because that information was 

not publicly available and members had no reason to ask about it. For that reason, this 

case is distinguishable from Doll.

The next two cases Oxy cites involved decertification motions. In both cases, the 

district court certified the class and the defendant later asked the court to decertify based 

on a statute-of-limitations defense predominating over individual questions. Blair v. 

TransAm Trucking, Inc., 309 F. Supp. 3d 977, 1012 (D. Kan. 2018); O'Connor v. Boeing 

North American, Inc., 197 F.R.D. 404, 413-14 (C.D. Cal. 2000). The O'Connor court, for 

example, noted that when it first certified the class, the plaintiffs' allegations "supported 

the inference that no one could reasonably have learned of [d]efendants' alleged" conduct 

until after the limitations period ran. 197 F.R.D. at 414. Cooper has similarly alleged that 

no class member could have known about Oxy's deductions because they were 

confidential. So Cooper may be able to prove equitable estoppel classwide. And if the 
32

district court later determines that Cooper cannot do so, then it can amend or decertify the 

class as necessary. See Chamberlain v. Farm Bureau Mut. Ins. Co., 36 Kan. App. 2d 163, 

177-78, 137 P.3d 1081 (2006).

Oxy's last case involved a class action filed by landowners against the operator of 

a chemical plant. The landowners alleged that contamination caused by the plant 

decreased their property values. LaBauve v. Olin Corp., 231 F.R.D. 632, 637-38 (S.D. 

Ala. 2005). The definition for one of the subclasses in the case included hundreds of

landowners within a 20- to 25-kilometer area around the chemical plant. The court listed 

nine factors it would have to consider to determine whether each landowner could defeat 

a statute-of-limitations defense. That painstaking process precluded a predominance 

finding. 231 F.R.D. at 674-75.

The painstaking fact-finding process described in LaBauve is unlike the simple 

statute-of-limitations inquiry here. Like the class in LaBauve, Cooper's class includes 

hundreds of members. Yet determining whether equitable estoppel applies to each of 

Cooper's class members will not require a multi-factor, individualized analysis. Cooper 

alleges that Oxy concealed the deductions it took. If that's true, then no class member 

could have timely discovered their claims. Like the rest of the federal cases Oxy cites, 

LaBauve is distinguishable. 

Oxy cited one more case in a letter submitted after briefing under Supreme Court

Rule 6.09 (2020 Kan. S. Ct. R. 39), In re Rail Freight Fuel Surcharge Antitrust Litig., 

934 F.3d 619 (D.C. Cir. 2019). Like the other cases Oxy cited, Rail Freight is 

distinguishable. 

In Rail Freight, a class of 16,065 shipping companies sued under federal anti-trust 

laws for damages caused by a price-fixing conspiracy among several freight railroads. 

Proving these federal claims required each shipping company to prove both an injury to 
33

its business and a causal link between that injury and the price-fixing conspiracy. Without 

common proof of these elements, the shipping companies would not be able to meet Rule 

23's predominance requirement. So they needed a way to prove classwide that the pricefixing conspiracy injured each company. 

To do so, they relied on an expert's regression model that provided an estimated 

damage amount for each company. The model controlled for seven variables used to 

calculate railroad prices, attempting "to isolate price increases attributable to the alleged 

conspiracy." 934 F.3d at 621. But the model returned thousands of false positives. 

Although the companies claimed that they were all harmed by the price-fixing 

conspiracy, the model refuted that claim. It said that 2,037 (12.7%) of the companies 

suffered no losses. So the district court would have had to determine individually whether 

those 2,037 companies were injured by the conspiracy. That individualized inquiry for 

thousands of companies would predominate over common questions, so the court 

affirmed the denial of class certification. 934 F.3d at 624-25.

Oxy cites Rail Freight as making clear "that even where the plaintiff intends to 

present class-wide evidence through an expert, the plaintiff must show that common 

issues predominate over individual issues." True enough, but the district court correctly 

found that the statute-of-limitations defense presented a common, classwide question. 

Unlike the Rail Freight plaintiffs, Cooper doesn't rely on statistical models to show 

liability. Cooper relies instead on Oxy's data showing the expenses it deducted from 

royalties. Oxy admits that it took those deductions but says they didn't violate any 

implied duties in Class Leases. But if they do, then every class member suffered an

injury. There's no comparable problem in determining liability classwide; there's no 

potential that any class members were uninjured if Cooper wins its arguments about 

marketability. And the district court found that to the extent litigating the equitable 

estoppel issue presented individual questions, those questions would not predominate.
34

The district court correctly found that Cooper could litigate the statute-oflimitations defense classwide with evidence from its expert that no class member could 

have known about the deductions. That evidence supports an inference of equitable 

estoppel classwide. So the district court did not abuse its discretion in finding that Oxy's 

defense was a common question. 

Even if the statute-of-limitations defense had presented individual questions, the 

district court also found that those questions would not predominate. That finding was 

supported by the court's observation that in Fawcett, a statute-of-limitations defense had 

been tried classwide on remand. Oxy says the district court should not have relied on 

Fawcett because there may have been circumstances there that allowed classwide 

resolution of the limitations defense that are not present here. But Oxy doesn't say what 

those circumstances are; we need not speculate about what they might be. The district 

court didn't abuse its discretion in finding that any individual questions posed by Oxy's 

limitations defense would not predominate over common questions.

Oxy raised one last point on predominance in its reply brief. Cooper's brief argued

that even if the statute of limitations bars several years of recovery for class members, it 

doesn't bar claims within the limitations period. Oxy frames that argument as Cooper

sacrificing the bulk of class members' potential claims (because most are outside the 

limitations period) to obtain certification. Oxy says this raises questions about the 

adequacy of Cooper as a class representative. Adequacy of representation is one of the 

four prerequisite requirements for class certification. K.S.A. 2019 Supp. 60-223(a)(4). 

Oxy didn't argue adequacy of representation in its original brief; it raised the issue for the 

first time in the reply brief. Cooper had no opportunity to respond, so we need not 

consider Ox's adequacy argument. Sierra Club v. Mosier, 305 Kan. 1090, Syl. ¶ 19, 391 

P.3d 667 (2017); see Supreme Court Rule 6.05 (2020 Kan. S. Ct. R. 36).
35

IV. The District Court Rigorously Analyzed the Requirements for Class Certification.

The last issue Oxy raises relates to the district court's treatment of expert 

testimony. Oxy argues that the district court failed to rigorously analyze the statutory 

requirements for class certification because it ignored problems with Cooper's expert 

report and failed to resolve Oxy's motion to strike that report before certifying the class. 

The district court abuses its discretion when it certifies a class action without 

rigorously analyzing the statutory requirements. Farrar, 43 Kan. App. 2d 871, Syl. ¶¶ 3-

4. But a rigorous analysis doesn't mean the district court must "conduct a mini-trial with 

extensive fact-finding before certifying . . . a class." Critchfield, 293 Kan. at 293. It 

simply means that the court must find that the plaintiff has enough evidence to conclude 

that certification is appropriate given the statutory requirements. Critchfield, 293 Kan. at 

295. Oxy argues that the district court failed to conduct a rigorous analysis in two ways, 

both of which relate to its treatment of expert testimony.

First, Oxy claims that the district court didn't rigorously analyze the certification 

requirements because it ignored several issues Oxy raised with Cooper's expert. Oxy 

raised those issues in a motion to strike included within its motion opposing certification. 

The motion to strike said that Cooper's expert ignored important differences in lease 

language when calculating damages and that he failed to account for factors affecting the 

marketability of Class Gas. Oxy repeats these arguments on appeal and says that the 

district court should have addressed them. According to Oxy, these flaws made the 

expert's classwide-damage calculations unreliable. 

Oxy's arguments against Cooper's expert go to the merits, not certification. Given 

our earlier conclusion that Class Gas was unmarketable until it was processed, Cooper's 

expert couldn't have erred in failing to account for the marketability factors cited by Oxy 

(because they are the same pre-processing factors we rejected earlier). As for Oxy's other 
36

criticisms, Cooper and Oxy both presented experts who analyzed the parties' claims and 

calculated potential damages. The district court didn't conclusively adopt either party's 

expert testimony; it merely found that Cooper's expert showed an ability to calculate 

classwide damages and address other issues common to all class members. If the case 

goes to trial, the fact-finder may accept Oxy's criticisms of Cooper's expert. But at the 

certification stage, the district court needed only to find that Cooper had presented 

enough evidence to satisfy the statutory requirements. The district court did not abuse its 

discretion in finding that Cooper had done so. 

Second, Oxy argues that the district court didn't conduct a rigorous analysis

because it certified the class without ruling on Oxy's pending motion to strike Cooper's 

expert. 

Cooper says the court didn't have to rule on the motion because Oxy didn't argue it 

at the hearing on the certification motion. The gist of Cooper's argument is that Oxy 

invited any error because it agreed that the district court should wait to rule on the expert 

motion until after certification. But the transcript from the hearing makes quick work of 

this argument. Oxy's counsel explicitly asked the district court at the hearing to consider 

the expert motion along with the certification motion. So Oxy didn't invite the district 

court to delay ruling on its motion until after certification.

Even so, the district court implicitly ruled on Oxy's motion by making detailed 

findings in the certification order addressing the substance of the motion. For example, 

the motion claimed that Cooper's expert incorrectly assumed that Kansas law requires 

Oxy to pay royalties based on the best available price. The certification order directly 

addressed that point with citations to Oxy's motion. The court found that no Class Lease 

contained language disclaiming the best-price duty and that whether Oxy breached that 

duty was a common question. The court also addressed Oxy's claim that Cooper's expert 

wrongly assumed the point at which gas becomes marketable. It found that none of Oxy's 
37

general marketability factors affected the marketability of Class Gas. The district court 

implicitly denied Oxy's motion by responding to the substantive claims in that motion in 

the certification order.

We don't think that the district court would have committed error by not ruling—

implicitly or explicitly—on Oxy's motion. Oxy argues for a procedural rule that the 

district court had to rule on the motion to strike before certifying the class. Yet the statute 

for class certification, K.S.A. 2019 Supp. 60-223, doesn't impose such a requirement. Nor 

do the cases interpreting that section. What those cases do tell us is that the district court 

need not "conduct a mini-trial with extensive fact-finding before certifying a class."

Critchfield, 293 Kan. 285, Syl. ¶ 2. 

In short, the district court conducted a rigorous analysis when it certified Cooper's 

class action. The court issued more than 20 pages of findings and showed that it had 

thoughtfully considered the parties' arguments. The court did not have to oversee a minitrial on the battle-of-the-experts at this stage; it merely had to determine that Cooper 

presented enough evidence to satisfy the class-action requirements. Because the court did 

so, it did not abuse its discretion.

We affirm the district court's judgment.