FOR PUBLICATION

UNITED STATES COURT OF APPEALS

FOR THE NINTH CIRCUIT

KATHLEEN SONNER, on behalf of 

herself and all others similarly 

situated,

Plaintiff-Appellant,

v.

PREMIER NUTRITION CORPORATION, 

FKA Joint Juice, Inc.,

Defendant-Appellee.

No. 18-15890

D.C. No.

3:13-cv-01271-

RS

OPINION

Appeal from the United States District Court

for the Northern District of California

Richard Seeborg, District Judge, Presiding

Argued and Submitted December 3, 2019

San Francisco, California

Filed June 17, 2020

Before: Carlos F. Lucero,* Consuelo M. Callahan,

and Bridget S. Bade, Circuit Judges.

Opinion by Judge Bade

* The Honorable Carlos F. Lucero, United States Circuit Judge for 

the U.S. Court of Appeals for the Tenth Circuit, sitting by designation.
2 SONNER V. PREMIER NUTRITION CORP.

SUMMARY**

Restitution 

The panel affirmed on different grounds the district 

court’s dismissal of plaintiff’s claims for restitution where 

plaintiff failed to demonstrate that she lacked an adequate 

legal remedy.

Plaintiff brought a diversity action and sought $32 

million on behalf of a class of consumers, but as equitable 

restitution rather than as damages. The district court applied 

its interpretation of California law and dismissed plaintiff’s 

claims for restitution because there was an adequate remedy 

at law, i.e., damages, available.

The panel held, as a threshold jurisdictional issue, that 

pursuant to Erie Railroad Co. v. Tompkins, 304 U.S. 64 

(1938), and Guaranty Trust Co. of New York v. York, 326 

U.S. 99 (1945), federal courts must apply equitable 

principles derived from federal common law to claims for 

equitable restitution under California’s Unfair Competition 

Law and Consumers Legal Remedies Act (“CLRA”). The 

panel held that state law cannot circumscribe a federal 

court’s equitable powers even when state law affords the rule 

of decision.

The panel held that the district court did not abuse its 

discretion in denying plaintiff leave to amend her complaint 

for a third time to reallege the CLRA damages claim.

** This summary constitutes no part of the opinion of the court. It 

has been prepared by court staff for the convenience of the reader.
SONNER V. PREMIER NUTRITION CORP. 3

COUNSEL

Leslie E. Hurst (argued), Timothy G. Blood, Thomas J. 

O’Reardon II, and Paula R. Brown, Blood Hurst & 

O’Reardon LLP, San Diego, California; Todd D. Carpenter, 

Carlson Lynch Sweet Kilpela & Carpenter LLP, San Diego, 

California; Craig M. Peters, Altair Law, San Francisco, 

California; for Plaintiff-Appellant.

Jessica Grant (argued), Angel A. Garganta, and Brian A. 

Featherstun, Venable LLP, San Francisco, California, for 

Defendant-Appellee.

David M. Arbogast, Arbogast Law, San Carlos, California; 

Steven M. Bronson, The Bronson Firm APC, San Diego, 

California; for Amicus Curiae Consumer Attorneys of 

California.

Xavier Becerra, Attorney General; Nicklas A. Akers, Senior 

Assistant Attorney General; Michele Van Gelderen, 

Supervising Deputy Attorney General; Michael Reynolds, 

Deputy Attorney General; Office of the Attorney General, 

Los Angeles, California; for Amicus Curiae State of 

California.

OPINION

BADE, Circuit Judge:

On the brink of trial after more than four years of 

litigation, Plaintiff-Appellant Kathleen Sonner voluntarily 

dismissed her sole state law damages claim and chose to 

proceed with only state law equitable claims for restitution 

and injunctive relief. A singular and strategic purpose drove 

this maneuver: to try the class action as a bench trial rather 
4 SONNER V. PREMIER NUTRITION CORP.

than to a jury. Indeed, Sonner continued to seek $32,000,000 

on behalf of the consumers she represented, but as equitable 

restitution rather than as damages. But, to Sonner’s dismay, 

the plan backfired when, relying on its interpretation of 

California law, the district court dismissed her claims for 

restitution because an adequate remedy at law, i.e., damages, 

was available.

Pursuant to Erie Railroad Co. v. Tompkins, 304 U.S. 64 

(1938), and Guaranty Trust Co. of New York v. York, 

326 U.S. 99 (1945), we hold that federal courts must apply 

equitable principles derived from federal common law to 

claims for equitable restitution under California’s Unfair 

Competition Law (“UCL”) and Consumers Legal Remedies 

Act (“CLRA”).

I

In March 2013, Vincent Mullins filed a putative class 

action regarding “Joint Juice,” a nutritional product 

manufactured, marketed, and sold by Defendant-Appellee 

Premier Nutrition Corporation (“Premier”). After 

substituting as the proposed class representative and named 

plaintiff, Sonner amended the complaint in September 2014. 

In April 2016, the district court certified a class of all 

California consumers who had purchased Joint Juice since 

March 1, 2009.

The basis for the lawsuit is false advertising. In its 

marketing materials, Premier touts Joint Juice as a dietary 

supplement beverage that supports and nourishes cartilage, 

lubricates joints, and improves joint comfort.1

 But, 

1 We treat all factual allegations in the operative complaint as true. 

See Dougherty v. City of Covina, 654 F.3d 892, 897 (9th Cir. 2011).
SONNER V. PREMIER NUTRITION CORP. 5

according to Sonner, Joint Juice fails to provide its 

advertised health benefits.

As originally pleaded, the complaint demanded 

injunctive relief under the UCL and CLRA, restitution under 

the UCL and CLRA, and damages under an Illinois 

consumer protection statute. In the first amended complaint, 

Sonner dropped her claim under Illinois law and amended 

the CLRA claim to seek damages because Premier failed to 

correct the alleged CLRA violations pursuant to California 

Civil Code § 1782. Both complaints demanded a jury trial.

For years, the litigation proceeded in the typical fashion. 

Both sides took discovery, engaged in motion practice, and 

prepared for the looming jury trial. But less than two months 

before trial was scheduled to begin, and after defeating 

Premier’s summary judgment efforts, Sonner sought leave 

to file a second amended complaint to drop the CLRA 

damages claim. This strategy raises an obvious question: 

why would Sonner voluntarily abandon an ostensibly viable 

claim on the eve of trial after more than four years of 

litigation? The answer is also obvious: to request that the 

district court judge award the class $32,000,000 as 

restitution, rather than having to persuade a jury to award 

this amount as damages.

Premier opposed the motion for leave. Citing futility, 

Premier urged that Sonner’s proposed second amended 

complaint would require dismissal of the restitution claims 

pursuant to California’s inadequate-remedy-at-law doctrine. 

Without the CLRA damages claim, Premier argued, the 

proposed complaint failed to state viable claims for 

restitution because an adequate legal remedy—damages—

was available for that injury.
6 SONNER V. PREMIER NUTRITION CORP.

During oral argument on the motion, the district court 

admonished Sonner that if Premier successfully moved to 

dismiss the restitution claims, the court would not allow 

Sonner to amend her complaint for a third time to reallege 

the CLRA damages claim. The district court explained that 

allowing Sonner to reassert the intentionally dropped claim 

under such circumstances would reflect “total prejudice to 

the court system,” would be “unfair” and “prejudicial” to 

Premier, and would constitute an “abuse of the court 

system.”

The district court ultimately granted Sonner leave to 

amend and vacated the jury trial. Undeterred by Premier’s 

arguments and the district court’s warning, Sonner filed her 

second amended complaint in August 2017, dropping the

CLRA damages claim. And, true to its word, Premier moved 

to dismiss the restitution claims pursuant to Federal Rule of 

Civil Procedure 12(b)(6), arguing that Sonner needed to—

but could not—establish that she lacked an adequate legal 

remedy as required by both federal equitable principles and 

California law.

After full briefing and oral argument, the district court 

granted Premier’s motion to dismiss. Applying its 

interpretation of California law, the district court held that 

Sonner could not proceed on her equitable claims for 

restitution in lieu of a claim for damages. Specifically, the 

district court concluded that claims brought under the UCL 

and CLRA remained subject to California’s inadequateremedy-at-law doctrine, and that Sonner failed to establish 

that she lacked an adequate legal remedy for the same past 

harm for which she sought equitable restitution. The district 

court also denied Sonner’s request to amend her complaint 

to reallege the CLRA damages claim. After the district court 
SONNER V. PREMIER NUTRITION CORP. 7

entered judgment, Sonner timely appealed the order 

dismissing her claims for equitable restitution to this court.

We review the district court’s decision to grant a motion 

to dismiss under Rule 12(b)(6) de novo, Fayer v. Vaughn, 

649 F.3d 1061, 1063–64 (9th Cir. 2011) (per curiam), and to 

deny a request for leave to amend for abuse of discretion, 

DCD Progs., Ltd. v. Leighton, 833 F.2d 183, 186 (9th Cir. 

1987). We may affirm the district court’s dismissal of the 

complaint on any basis supported by the record. See 

Johnson v. Riverside Healthcare Sys., LP, 534 F.3d 1116, 

1121 (9th Cir. 2008).

II

Although not the basis for the district court’s decision, 

we must first resolve a threshold jurisdictional question: do 

federal equitable principles independently apply to Sonner’s 

equitable claims for restitution or must we, as a federal court, 

follow only the state law authorizing that equitable remedy?

Sonner argues that because her UCL and CLRA claims 

arise under California law and our jurisdiction rests in 

diversity, state law alone decides whether she must show a 

lack of an adequate legal remedy before obtaining restitution 

under those statutes. And, according to Sonner, the 

California legislature abrogated the state’s inadequateremedy-at-law doctrine for claims seeking equitable 

restitution under the UCL and CLRA.2

2 Sonner does not dispute that the restitution she seeks under the 

UCL and CLRA is restitution in equity, not restitution at law. See Great–

W. Life & Annuity Ins. Co. v. Knudson, 534 U.S. 204, 214 (2002) 

(drawing a “fine distinction between restitution at law and restitution in 

equity”). And California courts have held that “the UCL provides only
8 SONNER V. PREMIER NUTRITION CORP.

In contrast, Premier argues that federal courts in 

diversity are bound by traditional federal equitable 

principles, including the requirement that the party pursuing 

equitable relief establish that it lacks an adequate legal 

remedy. Premier also contends that equitable claims for 

restitution under the UCL and CLRA remain subject to 

California’s inadequate-remedy-at-law doctrine.

A

It has long been the province of federal courts sitting in 

equity to apply a body of federal common law irrespective 

of state law. See Russell v. Southard, 53 U.S. (12 How.) 139, 

147 (1851). Under the doctrine first prescribed in Erie, 

however, federal courts exercising diversity jurisdiction 

must follow state substantive law and federal procedural law 

when adjudicating state law claims. See Hanna v. Plumer, 

380 U.S. 460, 465 (1965). To carry out the thorny task of 

identifying whether a law is substantive or procedural, we 

generally use an “outcome-determination test,” which asks 

whether applying federal law instead of state law would 

“significantly affect” the litigation’s outcome. See 

Gasperini v. Ctr. for Humanities, Inc., 518 U.S. 415, 427 

(1996) (quoting York, 326 U.S. at 109). Thus, the outcome 

of a case in federal court should generally be “substantially 

the same, so far as legal rules determine the outcome of a 

litigation, as it would be if tried in a State court.” York, 

326 U.S. at 109.

for equitable remedies.” See Hodge v. Superior Court, 51 Cal. Rptr. 3d 

519, 523 (Ct. App. 2006); see also Nationwide Biweekly Admin., Inc. v. 

Superior Court, No. S250047, 2020 WL 2107914, at *1 (Cal. 2020) 

(concluding that the “causes of action established by the UCL” are 

“equitable in nature”).
SONNER V. PREMIER NUTRITION CORP. 9

But when deciding between state and federal law, we do 

not rely on a rote litmus test. See Hanna, 380 U.S. at 467. 

Rather, we must be cognizant of Erie’s dual aims: 

“discouragement of forum-shopping and avoidance of 

inequitable administration of the laws.” Gasperini, 518 U.S. 

at 428 (quoting Hanna, 380 U.S. at 468); see also Semtek 

Int’l Inc. v. Lockheed Martin Corp., 531 U.S. 497, 508–09 

(2001). And we should also consider the policies 

underpinning the applicable state and federal laws. See Byrd 

v. Blue Ridge Rural Elec. Coop., Inc., 356 U.S. 525, 537–38 

(1958).

B

As a result of Erie, the scope and application of federal 

common law narrowed considerably. See Tex. Indus., Inc. 

v. Radcliff Materials, Inc., 451 U.S. 630, 641 (1981) (noting 

that “absent some congressional authorization . . . federal 

common law exists only in . . . narrow areas”). 

Nevertheless, since Erie, the Supreme Court has instructed 

that a federal court’s equitable authority remains cabined to 

the traditional powers exercised by English courts of equity, 

even for claims arising under state law. See York, 326 U.S. 

at 104–07.

In York, the Court addressed whether a state’s statute of 

limitations could be asserted as a defense to an equitable 

claim arising under state law. See id. at 100–01, 107. When 

summarizing the applicability of Erie, the Court made clear 

that Congress provided that the forms and modes of 

proceeding in suits of equity should conform to the historic 

uses of courts of equity. See id. at 104–05. Writing for the 

Court, Justice Frankfurter explained:

In giving federal courts cognizance of 

equity suits in cases of diversity jurisdiction, 
10 SONNER V. PREMIER NUTRITION CORP.

Congress never gave, nor did the federal 

courts ever claim, the power to deny 

substantive rights created by State law or to 

create substantive rights denied by State law.

This does not mean that whatever 

equitable remedy is available in a State court 

must be available in a diversity suit in a 

federal court, or conversely, that a federal 

court may not afford an equitable remedy not 

available in a State court. Equitable relief in 

a federal court is of course subject to 

restrictions: the suit must be within the 

traditional scope of equity as historically 

evolved in the English Court of Chancery; a 

plain, adequate and complete remedy at law 

must be wanting; explicit Congressional 

curtailment of equity powers must be 

respected; [and] the constitutional right to 

trial by jury cannot be evaded. That a State 

may authorize its courts to give equitable 

relief unhampered by any or all such 

restrictions cannot remove these fetters from 

the federal courts.

Id. at 105–06 (internal quotation marks and citations 

omitted) (emphases added). The Court further instructed 

that “State law cannot define the remedies which a federal 

court must give simply because a federal court in diversity 

jurisdiction is available as an alternative tribunal to the 

State’s courts.” Id. at 106; see also Pusey & Jones Co. v.

Hanssen, 261 U.S. 491, 497–98 (1923) (“That a remedial 

right to proceed in a federal court sitting in equity cannot be 

enlarged by a state statute is likewise clear. . . . The federal 
SONNER V. PREMIER NUTRITION CORP. 11

court may therefore be obliged to deny an equitable remedy 

which the plaintiff might have secured in state court.”).

The Court also explained that “[t]he source of 

substantive rights enforced by a federal court under diversity 

jurisdiction . . . is the law of the States.” York, 326 U.S.

at 112. Federal courts must therefore enforce “State-created 

substantive rights if the mode of proceeding and remedy 

[are] consonant with the traditional body of equitable 

remedies, practice and procedure.” Id. at 106.

C

In accordance with York, we hold that a federal court 

must apply traditional equitable principles before awarding 

restitution under the UCL and CLRA. It has been a 

fundamental principle for well over a century that state law 

cannot expand or limit a federal court’s equitable authority. 

See Payne v. Hook, 74 U.S. (7 Wall.) 425, 430 (1868) (“The 

equity jurisdiction conferred on the Federal courts is the 

same that the High Court of Chancery in England possesses; 

is subject to neither limitation or restraint by State 

legislation, and is uniform throughout the different States of 

the Union.”). Erie intervened in 1938, of course, and the 

merger of law and equity followed soon after. But in 

seventy-five years, the Supreme Court has never repudiated 

its statements in York—offered seven years after Erie—that 

state law can neither broaden nor restrain a federal court’s 

power to issue equitable relief.3

3 We recognize that the statute York cited to support the principle 

that a “plain, adequate and complete remedy at law must be wanting,”

326 U.S. at 105, was repealed in 1948 after the merger of law and equity, 

see 28 U.S.C. § 384 (repealed 1948). That merger does not, however,

affect the validity of the principle. See, e.g., Grupo Mexicano de 
12 SONNER V. PREMIER NUTRITION CORP.

To be sure, York suggests that the “outcome” of a lawsuit 

should be “substantially the same” regardless of whether it 

is filed in state or federal court, 326 U.S. at 109, and applying 

federal equitable principles may lead to a different result if, 

as Sonner contends, California abrogated its inadequateremedy-at-law requirement for claims brought under the 

UCL and CLRA. But the Supreme Court clearly foresaw the 

possibility of this sort of inconsistency in York and 

concluded that federal courts must nonetheless apply 

principles of federal common law. See id. at 105–06. 

According to the Court, even if a state authorizes its courts 

to provide equitable relief when an adequate legal remedy 

exists, such relief may be unavailable in federal court 

because equitable remedies are subject to traditional 

equitable principles unaffected by state law. See id. at 105–

06 & n.3.4

 Since York, the Court has never held or suggested 

Desarrollo S.A. v. All. Bond Fund, Inc., 527 U.S. 308, 322 (1999)

(“Notwithstanding the fusion of law and equity by the Rules of Civil 

Procedure, the substantive principles of Courts of Chancery remain

unaffected.” (quoting Stainback v. Mo Hock Ke Lok Po, 336 U.S. 368, 

382 n.26 (1949))); Oneida Indian Nation of N.Y. State v. Cty. of Oneida, 

464 F.2d 916, 922 (2d Cir. 1972) (“While [York] relied on § 16 of the 

Judiciary Act of 1789 (later Rev. Stat. § 723 and 28 U.S.C. § 384 (1940 

ed.)), which limited suits in equity to cases in which there was no ‘plain, 

adequate and complete remedy’ at law, and that statute was repealed in 

1948 as obsolete in view of the merger of law and equity under the 

Federal Rules of Civil Procedure, 62 Stat. 992, the principle remains 

intact.”), rev’d on other grounds, 414 U.S. 661 (1974).

4 Sonner characterizes the Court’s statements in York regarding 

equitable remedies as dicta, and some courts have endorsed that view. 

See New Mexico ex rel. Balderas v. Real Estate Law Ctr., P.C., 401 F. 

Supp. 3d 1229, 1349 n.93 (D.N.M. 2019); Bangor Baptist Church v. 

State of Me., Dep’t of Educ. & Cultural Servs., 576 F. Supp. 1299, 1314

& n.21 (D. Me. 1983). Even if we construe these statements as dicta, we 

must “afford [them] a weight that is greater than ordinary judicial dicta 

as prophecy of what the [C]ourt might hold.” Nettles v. Grounds, 
SONNER V. PREMIER NUTRITION CORP. 13

that state law can expand a federal court’s equitable powers, 

even if allowing such expansion would ensure a similar 

outcome between state and federal tribunals.

Additionally, the “outcome” of this litigation is not our 

“only consideration” as we must also balance the policies 

underlying the state and federal laws. See Byrd, 356 U.S. at 

537–38. Here, as in Byrd, the principle precluding courts 

from awarding equitable relief when an adequate legal 

remedy exists implicates the well-established federal policy 

of safeguarding the constitutional right to a trial by jury in 

federal court. See id. at 537–39 (state rules should not 

abridge a constitutional right to a jury trial in federal court); 

see also Scott v. Neely, 140 U.S. 106, 110 (1891) 

(“[W]henever, respecting any right violated, a court of law 

is competent to render a judgment affording a plain, 

adequate, and complete remedy, the party aggrieved must 

seek his remedy in such court . . . because the defendant has 

a constitutional right to a trial by jury . . . .”). Even assuming 

California decided as a matter of policy to streamline UCL 

and CLRA claims by abrogating the state’s inadequateremedy-at-law doctrine, the strong federal policy protecting 

the constitutional right to a trial by jury outweighs that 

procedural interest.

Sonner cites our decision in Sims Snowboards, Inc. v. 

Kelly, 863 F.2d 643 (9th Cir. 1988), to argue that a federal 

court sitting in diversity applies state law to determine the 

availability of equitable relief. But Sims does not control 

830 F.3d 922, 930-31 (9th Cir. 2016) (en banc) (quoting Managed 

Pharmacy Care v. Sebelius, 716 F.3d 1235, 1246 (9th Cir. 2013)). And 

“[a]s a lower federal court, we are advised to follow the Supreme Court’s 

considered dicta.” Lemoge v. United States, 587 F.3d 1188, 1193 (9th 

Cir. 2009) (quoting Fernandez-Ruiz v. Gonzales, 466 F.3d 1121, 1129 

(9th Cir. 2006) (en banc)).
14 SONNER V. PREMIER NUTRITION CORP.

here. In that diversity action, the district court awarded the 

plaintiff a preliminary injunction under Federal Rule of Civil 

Procedure 65 despite a California statute expressly 

prohibiting the issuance of an injunction under the 

circumstances. Id. at 646. We reversed and held that 

because “the outcome [of the case] is in large part 

determined at the preliminary injunction stage,” state law 

controls whether a federal court should grant preliminary 

injunctive relief. Id. at 647. And in accord with York, we 

noted that “[t]he general equitable powers of federal courts 

should not enable a party suing in diversity to obtain an 

injunction if state law clearly rejects the availability of that 

remedy.” Id.; see York, 326 U.S. at 110 (“Plainly enough, a 

statute that would completely bar recovery in a suit if 

brought in a State court bears on a State created right vitally 

and not merely formally or negligibly. As to consequences 

that so intimately affect recovery or non-recovery a federal 

court in a diversity case should follow State law.”).

In contrast to Sims, we must now decide whether a 

federal court sitting in diversity can award equitable 

restitution under state law if an adequate legal remedy exists. 

Injunctive relief is not at issue, nor is Sonner exploiting the 

federal judiciary to access a remedy that California “clearly 

rejects.” See Sims, 863 F.2d at 647. Our inquiry instead 

aligns directly with the rigid restrictions on a federal court’s 

equitable powers explicitly enumerated in York. Indeed, 

since Sims, we have confirmed that a state “statute does not 

change the nature of the federal courts’ equitable powers.” 

See Can. Life Assurance Co. v. LaPeter, 563 F.3d 837, 843 

(9th Cir. 2009) (holding that federal equitable principles 

govern the appointment of a receiver independent of state 

law); see also Barranco v. 3D Sys. Corp., 952 F.3d 1122, 

1129 (9th Cir. 2020) (recognizing, in a diversity action 

where state law allowed equitable relief, that “‘[t]he 
SONNER V. PREMIER NUTRITION CORP. 15

necessary prerequisite’ for a court to award equitable 

remedies is ‘the absence of an adequate remedy at law’” 

(quoting Dairy Queen, Inc. v. Wood, 369 U.S. 469, 478 

(1962))).5

Finally, our decision mirrors those of several other 

circuits, which have concluded, consistent with York, that 

state law cannot circumscribe a federal court’s equitable 

powers even when state law affords the rule of decision. See 

Davilla v. Enable Midstream Partners L.P., 913 F.3d 959, 

972–73 (10th Cir. 2019) (“The Supreme Court has 

concluded that ‘State law cannot define the remedies which 

a federal court must give’ . . . . Thus, the practice of 

borrowing state rules of decision does not apply with equal 

force to determining appropriate remedies, especially 

equitable remedies, as it does to defining actionable rights.” 

(quoting York, 326 U.S. at 105));6 SSMC, Inc., N.V. v. 

5 Sonner’s reliance on McKesson HBOC, Inc. v. New York State 

Common Retirement Fund, Inc., 339 F.3d 1087 (9th Cir. 2003), likewise 

does not support her desired outcome. McKesson addressed neither Erie

nor York, and the court simply assumed that state law governed the 

availability of equitable remedies. See 339 F.3d at 1093-94. We thus 

are not bound by that decision. See, e.g., Galam v. Carmel (In re Larry’s 

Apartment, L.L.C.), 249 F.3d 832, 839 (9th Cir. 2001) (“[Q]uestions 

which merely lurk in the record, neither brought to the attention of the 

court nor ruled upon, are not to be considered as having so decided as to 

constitute precedents.” (quoting Webster v. Fall, 266 U.S. 507, 511 

(1925))); Lum v. City & Cty. of Honolulu, 963 F.2d 1167, 1170 n.1 (9th 

Cir. 1992) (noting that cases which “stumble into decisions on questions 

neither raised nor discussed by the parties or by the trial court are not 

treated as authoritative on those unstated assumptions and nonlitigated 

points”).

6 Prior to Davilla, then-Judge Gorsuch observed that “[w]hen 

addressing cases arising under the diversity statute, we’ve seen the 

Supreme Court has likewise suggested that diversity authority doesn’t 

necessarily endow federal district courts the power or authority to issue 
16 SONNER V. PREMIER NUTRITION CORP.

Steffen, 102 F.3d 704, 708 (4th Cir. 1996) (rejecting the 

argument that district court erred in issuing a remedy beyond 

what state law permitted because “[s]tate law cannot define 

the remedies which a federal court must give simply because 

a federal court in diversity jurisdiction is available as an 

alternative tribunal to the State’s courts” (alteration in 

original) (quoting York, 326 U.S. at 106)); Perfect Fit Indus., 

Inc. v. Acme Quilting Co., 646 F.2d 800, 806 (2d Cir. 1981) 

(“State law does not govern the scope of the equity powers 

of the federal court; and this is so even when state law 

supplies the rule of decision.”); Oneida Indian Nation of N.Y. 

State, 464 F.2d at 922 (holding that “[i]t is settled that federal 

courts may not apply state statutes expanding equity 

jurisdiction beyond that prevailing when the Constitution 

was adopted,” including “cases in which there was no ‘plain, 

adequate and complete remedy at law’”); Clark Equip. Co. 

v. Armstrong Equip. Co., 431 F.2d 54, 57 (5th Cir. 1970) 

(“Federal courts in diversity cases [have] the power to 

enforce State-created substantive rights by well-recognized 

equitable remedies even though such remedy might not be 

available in the courts of the State.”); Hertz v. Record Publ’g 

Co. of Erie, 219 F.2d 397, 398 n.2 (3d Cir. 1955) (“Federal 

remedies are not limited or affected by state law.”); see also 

Nat’l P’ship Inv. Corp. v. Nat’l Hous. Dev. Corp., 153 F.3d 

1289, 1291–92 (11th Cir. 1998) (citing Pusey & Jones and 

York to hold that federal law governs the appointment of a 

receiver in a diversity case because the equitable remedy of 

receivership is not a substantive right); Aviation Supply 

Corp. v. R.S.B.I. Aerospace, Inc., 999 F.2d 314, 316 (8th Cir. 

1993) (holding that federal law and federal equitable 

every form of equitable relief a state court might possess in the same 

situation.” Niemi v. Lasshofer, 728 F.3d 1252, 1259 (10th Cir. 2013) 

(citing York, 326 U.S. at 105).
SONNER V. PREMIER NUTRITION CORP. 17

principles govern the appointment of a receiver in a diversity 

case).

At bottom, “[t]hat a State may authorize its courts to give 

equitable relief unhampered by” the “restriction[]” that an 

adequate remedy at law be unavailable “cannot remove 

th[at] fetter[] from the federal courts.” York, 326 U.S. 

at 105–06. Guided by that instruction, we hold that the 

traditional principles governing equitable remedies in 

federal courts, including the requisite inadequacy of legal 

remedies, apply when a party requests restitution under the 

UCL and CLRA in a diversity action.7

D

Under these principles, Sonner must establish that she 

lacks an adequate remedy at law before securing equitable 

restitution for past harm under the UCL and CLRA. See 

Mort v. United States, 86 F.3d 890, 892 (9th Cir. 1996) (“It 

is a basic doctrine of equity jurisprudence that courts of 

equity should not act . . . when the moving party has an 

adequate remedy at law.” (ellipsis in original) (quoting 

Morales v. Trans World Airlines, Inc., 504 U.S. 374, 381 

(1992))); see also, e.g., Franklin v. Gwinnett Cty. Pub. Sch., 

503 U.S. 60, 75–76 (1992) (holding that when “remedies are 

7 We need not linger long on Sonner’s argument that “under federal 

law” we look to the legislature’s intent with respect to “whether a statute 

provides for equitable remedies irrespective of an adequate-remedy-atlaw.” The cases Sonner cites apply when equitable relief is sought under 

a federal statute, not a state statute. See United States v. Oakland 

Cannabis Buyers’ Coop., 532 U.S. 483, 497 (2001) (addressing 

injunctions under the Controlled Substances Act); Weinberger v. 

Romero-Barcelo, 456 U.S. 305, 316 (1982) (addressing injunctions 

under the Federal Water Pollution Control Act). Federal equitable 

principles are not subject to qualification by the intent of California’s 

legislature.
18 SONNER V. PREMIER NUTRITION CORP.

equitable in nature . . . it is axiomatic that a court should 

determine the adequacy of a remedy in law before resorting 

to equitable relief”); Schroeder v. United States, 569 F.3d 

956, 963 (9th Cir. 2009) (“[E]quitable relief is not 

appropriate where an adequate remedy exists at law.”).

Sonner fails to make such a showing. Initially, the 

operative complaint does not allege that Sonner lacks an 

adequate legal remedy. See O’Shea v. Littleton, 414 U.S. 

488, 502 (1974) (holding that a complaint seeking equitable 

relief failed because it did not plead “the basic requisites of 

the issuance of equitable relief” including “the inadequacy 

of remedies at law”). More importantly, Sonner concedes 

that she seeks the same sum in equitable restitution as “a full 

refund of the purchase price”—$32,000,000—as she 

requested in damages to compensate her for the same past 

harm. Sonner fails to explain how the same amount of 

money for the exact same harm is inadequate or incomplete, 

and nothing in the record supports that conclusion.8

Accordingly, because Sonner fails to establish that she 

lacks an adequate remedy at law, we hold, albeit on 

alternative grounds, that the district court did not err in 

8 Sonner’s citation to American Life Insurance Co. v. Stewart, 

300 U.S. 203, 214 (1937), is unavailing. There, the Court held that “[a] 

remedy at law does not exclude one in equity unless it is equally prompt 

and certain and in other ways efficient.” Id. But Sonner fails to explain 

how damages are any less prompt, certain, or efficient than restitution, 

particularly when a jury trial for damages was just two months away 

when she amended her complaint. Likewise, that California enacted the 

UCL to create new “remedies” not “available at common law,” see 

Nationwide Biweekly Admin., Inc., 2020 WL 2107914 at *21, is not 

dispositive because it does not account for subsequently enacted statutes, 

such as the CLRA.
SONNER V. PREMIER NUTRITION CORP. 19

dismissing Sonner’s claims for equitable restitution under 

the UCL and CLRA.

III

Turning to the final issue before us, we conclude that the 

district court did not abuse its discretion in denying Sonner 

leave to amend her complaint for a third time to reallege the 

CLRA damages claim. Sonner strategically chose to amend 

her complaint on the eve of trial to drop her damages claim. 

Premier opposed Sonner’s request to amend, arguing that 

Sonner needed to establish a lack of legal remedy before 

seeking equitable restitution and warning that it would file a 

motion to dismiss on that basis. The district court then 

cautioned Sonner prior to the amendment that it would not 

permit her to reallege the damages claim because allowing 

her to do so would be unfair, prejudicial, and an affront to 

the judicial system. Under these circumstances, the district 

court did not abuse its “particularly broad” discretion in 

denying leave to amend. See Chodos v. W. Publ’g Co., 

292 F.3d 992, 1003 (9th Cir. 2002) (citation omitted); see 

also AmerisourceBergen Corp. v. Dialysist W., Inc., 

465 F.3d 946, 951 (9th Cir. 2006) (“[A] district court need 

not grant leave to amend where the amendment: 

(1) prejudices the opposing party; (2) is sought in bad faith; 

(3) produces an undue delay in litigation; or (4) is futile.”).

IV

Regardless of whether California authorizes its courts to 

award equitable restitution under the UCL and CLRA when 

a plain, adequate, and complete remedy exists at law, we 

hold that federal courts rely on federal equitable principles 

before allowing equitable restitution in such circumstances. 

And because Sonner fails to demonstrate that she lacks an 
20 SONNER V. PREMIER NUTRITION CORP.

adequate legal remedy in this case, we affirm the district 

court’s order dismissing her claims for restitution.9

AFFIRMED.

9 We deny Sonner’s request for judicial notice, and motion to certify 

a question to the California Supreme Court, because neither is relevant 

to the resolution of this appeal. See Santa Monica Food Not Bombs v. 

City of Santa Monica, 450 F.3d 1022, 1025 n.2 (9th Cir. 2006).