<PAGE>

                                                                   Exhibit 99(a)

                  AMENDED AND RESTATED SHAREHOLDERS' AGREEMENT

                  THIS AMENDED AND RESTATED SHAREHOLDERS' AGREEMENT, dated as of
July 19, 2000, by and among Newhall Management Corporation, a California
corporation and formerly known as New Newhall Management Corporation (the
"Company"), the person who from time to time shall serve as the Secretary of the
Company and trustee of a voting trust created pursuant to a Voting Trust
Agreement dated November 14, 1990 (as amended, the "Voting Trust Agreement")
(the "Trustee"), and George L. Argyros, Gary M. Cusumano, Thomas L. Lee, Thomas
V. McKernan, Jr., Henry K. Newhall, Jane Newhall, Peter T. Pope, Carl E.
Reichardt, Thomas C. Sutton, Barry Lawson Williams, and Ezra K. Zilkha (the
"Shareholders"). This Agreement hereby amends and restates in its entirety the
Shareholders' Agreement dated November 14, 1990 by the parties hereto, as
amended by that certain Amendment to Shareholders' Agreement dated as of
November 20, 1991 ("Prior Shareholders' Agreement").

                                   WITNESSETH:

                  WHEREAS, the Company is the Managing General Partner of
Newhall Management Limited Partnership (the "Partnership"), which is the
Managing General Partner of The Newhall Land and Farming Company (a California
Limited Partnership) ("Newhall"); and

                  WHEREAS, the Shareholders beneficially own all of the issued
and outstanding stock of the Company; and

                  WHEREAS, simultaneously with the execution of the Prior
Shareholders' Agreement all the Shareholders have entered into the Voting Trust
Agreement, providing for the voting of the Common Stock of the Company; and

                  WHEREAS, all of the Shareholders together constitute all of
the directors of the Company; and

                  WHEREAS, the parties hereto desire to promote their mutual
interest and the interests of the Company and the Partnership by imposing
certain restrictions upon the ownership and transferability of the Common Stock
of the Company; and

                  WHEREAS, the Shareholders wish to amend and restate the Prior
Shareholders' Agreement to permit transfers of beneficial ownership of the
Common Stock of the Company to a living trust for the exclusive benefit of the
Shareholders for estate planning purposes:

                  NOW, THEREFORE, the parties hereby agree as follows:

                                    ARTICLE 1

                                     SHARES

                  Section 1.1       SHARES.  This Agreement applies to all
shares of Common Stock and any other equity securities of the Company and to any
Voting Trust Certificates issued pursuant to the Voting Trust Agreement and the
interests represented by the Voting Trust Certificates. Each share of Common
Stock and any other equity security of the Company, including any equity
securities issued as a dividend or other distribution with respect to such
shares or securities, and the rights to receive such shares and securities and
any interests which are represented by a Voting Trust Certificate, shall be
deemed to be a "Share" under this Agreement and are collectively referred to as
"Shares."


                                       1
<PAGE>

                                    ARTICLE 2

                                  contributions

                  Section 2.1       CAPITAL CONTRIBUTION.

                           (a)      Each Shareholder represents that he or she
has contributed to the capital of the Company the number of Units set forth
opposite his or her name below and has received one Share for each Unit so
contributed:

<TABLE>
<CAPTION>
                                                       No. of
                               Shareholder              Units
                               -----------             ------
<S>                                                       <C>
               George L. Argyros                            350
               Gary M. Cusumano                             350
               Thomas L. Lee                                370
               Thomas V. McKernan, Jr.                      350
               Henry K. Newhall                             370
               Jane Newhall                                  20
               Peter T. Pope                                350
               Carl E. Reichardt                            370
               Thomas C. Sutton                             350
               Barry Lawson Williams                        350
               Ezra K. Zilkha                               370
                                                          -----
                        Total                             3,600
</TABLE>

                           (b)      The Shareholders understand that the
directors of the Company intend that distributions, if any, by the Partnership
with respect to Units contributed to the capital of the Company will be declared
as dividends of the Company.

                                    ARTICLE 3

                         REPRESENTATIONS AND WARRANTIES
                                 OF SHAREHOLDERS

                  Section 3.1       REPRESENTATIONS AND WARRANTIES.  Each
Shareholder represents and warrants that:

                           (a)      Subject to the Voting Trust Agreement, he or
she is the owner of the number of Shares set forth opposite his or her name on
the signature line of this Agreement, free and clear of all liens and
encumbrances, and there are no outstanding options, agreements, contracts,
calls, commitments or demands of any character to which the Shareholder is a
party or of which the Shareholder knows, which restrict or require the transfer
of, or otherwise relate to, the Shares, except this Agreement, the Voting Trust
Agreement, and the Bylaws of the Company, and

                           (b)      He or she is acquiring the Shares for
investment and not with a view to or for resale in connection with any
distribution of the Shares.

                                    ARTICLE 4

                                    TRANSFER

                  Section 4.1       RESTRICTION ON TRANSFER.


                                       2
<PAGE>

                           (a)      Except as provided in this Agreement, no
Shareholder or holder of a Voting Trust Certificate ("Certificate Holder") will
sell, assign, transfer, convey, pledge, hypothecate, give a security interest
in, encumber, give, or otherwise dispose or attempt to dispose of any of the
Shares or any interest therein (all of the foregoing are herein referred to as a
"Transfer"); provided, however, that the Shareholder may transfer the Shares to
a trustee of a revocable inter vivos trust for the exclusive benefit of the
Shareholder and the Shareholder's spouse which qualifies under Section 1361(c)
of the Code as a permissible Shareholder of a corporation qualified under
Subchapter S of the Code ("Permitted Transfer" and the transferee shall be
referred to as "Permitted Transferee"). Any purported Transfer of any Shares
contrary to this Agreement shall be null and void, and the purported purchaser
or other transferee shall acquire no interest whatsoever in such Shares.

                           (b)      Each person to whom Shares are transferred
by means of the Permitted Transfer specified in Section 4.1(a) hereof must, as a
condition precedent to the validity of such transfer, acknowledge in writing to
the Company that such person is bound by the provisions of this Agreement and
that the transferred shares are subject to the Company's transferability
restrictions, to the same extent the Shares would be so subject if retained by
the Shareholder.

                           (c) For purposes of this Agreement the term "Owner"
shall include the Shareholder and all subsequent holders of the Shares who
derive their chain of ownership through a Permitted Transfer from the
Shareholder in accordance with Section 4.1(a) hereof. The term "Owner" shall not
include transferees pursuant to Section 4.4. The term "Respective Shareholder"
shall mean the Shareholder, and or, in the event of Permitted Transfer, the
Shareholder who transferred the Shares to the Owner.

                  Section 4.2       REPURCHASE EVENT.

                           (a)      As to each Owner, any of the following
events constitutes a "Repurchase Event":

                                    (i)     the Respective Shareholder ceases to
be a director of the Company for any reason;

                                    (ii) the Owner fails to re-execute the
Voting Trust Agreement, as provided in the Voting Trust Agreement, as it may be
amended from time to time;

                                    (iii) any Shares held by an Owner are levied
upon under a writ of execution, become subject to sale under any legal process,
are transferred or ordered to be transferred to or for the benefit of any person
or entity as a result of or in connection with any final property settlement or
judgment incident to a divorce, dissolution of marriage, or separation or are
transferred or ordered to be transferred to any person by decree of distribution
or other court order in proceedings arising from the death of the spouse of any
Owner (on and as of the date of such levy, legal process, settlement, judgment,
decree, or order);

                                    (iv) the Shareholder, together with his or
her Permitted Transferees, fails to own at least one limited partner unit in the
Partnership;

                                    (v)     a Transfer or attempted or purported
Transfer in violation of Section 4.1 occurs;

                                    (vi) the Shareholder fails to make a
contribution to capital as set forth in Section 2.1(a);


                                       3
<PAGE>

                                    (vii) the Owner fails to sign a consent to
the Company's election under Subchapter S of the Internal Revenue Code of 1986,
as amended (the "Code"), whenever such consent may be requested by the Company;

                                    (viii) the Owner's spouse, if applicable,
fails to sign any consent which may be required; or

                                    (ix) the Owner or Respective Shareholder
materially breaches this Agreement or the Voting Trust Agreement.

                           (b)      Upon the occurrence of any Repurchase Event:

                                    (i)     the owner of the Shares subject to
the Repurchase Event shall promptly notify the Company of the Repurchase Event;

                                    (ii) the Respective Shareholder subject to
the Repurchase Event shall resign immediately as a Director of the Company; and

                                    (iii) the Company shall repurchase (or
otherwise direct the sale of) all Shares owned by the Owner and Respective
Shareholder in accordance with Section 4.3 within one year from the Repurchase
Event and the Company shall use its best efforts to repurchase such Shares as
soon as possible after the Repurchase Event.

                  Section 4.3       REPURCHASE OF SHARES.

                           (a)      The Company shall repurchase the Shares of
an Owner as follows:

                                    (i)     The purchase price per Share
repurchased by the Company shall be an amount equal to the then current market
value of one unit representing a limited partnership unit of Newhall ("Public
Unit"), as adjusted to reflect splits, recapitalizations, or like events, which
may have occurred after the issuance of the Shares and which were not reflected
in a corresponding split in the Shares. The market value of one Public Unit of
Newhall shall be deemed to be the closing trading price of a Public Unit on the
New York Stock Exchange on the last trading day immediately preceding the
repurchase.

                                    (ii) Subject to Section 4.2(b)(iii), the
Shares shall be repurchased at such time or times as the Company shall
determine. In connection with any such repurchase, the appropriate number of
Shares shall be withdrawn from the voting trust and surrendered to the Company
for cancellation.

                           (b)      Notwithstanding anything to the contrary
herein, if a Repurchase Event occurs, the Company may approve or require the
sale of the Shares by an Owner directly or indirectly to his or her successor as
director at a price per Share equal to that set forth in Section 4.3(a)(i)
hereof.

                  Section 4.4       TRANSFER PURSUANT TO ADDITION OF DIRECTOR.
If approved by the Board of Directors of the Company, a Shareholder may transfer
Shares owned by the Shareholder directly or indirectly to a new or existing
director at a price per Share equal to that set forth in Section 4.3(a)(i)
hereof.


                                       4
<PAGE>

                                    ARTICLE 5

                            LEGEND; SPOUSAL AGREEMENT

                  Section 5.1       LEGEND. The Company will transfer Shares on
its books only in accordance with the terms and conditions of this Agreement and
the Voting Trust Agreement. The Trustee will transfer Voting Trust Certificates
only on his books and only in accordance with the terms and conditions of this
Agreement and the Voting Trust Agreement. Certificates representing Shares of
the Company held pursuant to the Voting Trust Agreement and each of the Voting
Trust Certificates shall bear a legend in the form of Exhibit A hereto.

                  Section 5.2       SPOUSAL AGREEMENT. The spouse of each
Shareholder shall execute a Consent and Agreement of Spouse in the form attached
hereto as Exhibit B, if the respective Spouse has not previously consented to
any amendment of the Prior Shareholders' Agreement.

                                    ARTICLE 6

                               ADDITIONAL PARTIES

                  Section 6.1       ADDITIONAL PARTIES. The parties hereto agree
and consent in advance that upon the election of a replacement director to the
Board of Directors of the Company, who is not already a party to this Agreement,
such new director shall, upon agreeing in writing to be bound by the terms and
provisions of this Agreement and the Voting Trust Agreement, and upon the
purchase of Shares from a prior Shareholder (including Shares held by
Shareholder and his or her Permitted Transferees) pursuant to Section 4.3(b) or
Section 4.4 or the purchase from the Company for cash of the number of Shares
owned by the leaving director, become a party to this Agreement. The parties
hereto agree and consent in advance that upon the election of a new director,
such new director shall, upon agreeing in writing to be bound by the terms and
provisions of this Agreement and the Voting Trust Agreement, and upon the
purchase of a number of Shares specified by the directors in their sole
discretion at a price per Share equal to that set forth in Section 4.3(a)(i)
hereof, become a party to this Agreement. In the event other persons become
parties to this Agreement, this Agreement will continue to be binding upon every
Owner of the Company without the re-execution of, or amendment to this
Agreement.

                  Section 6.2       PARTNERSHIP UNITS. Each new director shall
own at least one limited partner unit in the Partnership and the failure to own
at least one limited partner unit in the Partnership is a Repurchase Event under
Section 4.2(a).

                                    ARTICLE 7

                                   TERMINATION

                  Section 7.1       TERMINATION.

                           (a)      This Agreement shall terminate as to all
parties if the Company shall cease for any reason to be the Managing General
Partner of the Partnership, or the Partnership shall cease for any reason to be
the Managing General Partner of Newhall, or if all parties to this Agreement
consent to its termination.

                           (b)      This Agreement shall terminate as to an
individual Owner upon the repurchase of all of his or her Shares pursuant to
this Agreement. No termination as to any Owner shall cause or constitute a
termination of this Agreement as to any other Owner.

                           (c) This Agreement may only be terminated pursuant to
this Section 7.1.


                                       5
<PAGE>

                                    ARTICLE 8

                                     NOTICES

                  Section 8.1       NOTICES. Any notice, request, instruction,
or other document to be given by any party to another party shall be in writing
and shall be deemed given at the time it is deposited in the United States
mails, postage prepaid, by registered or certified mail, at the time it is
personally delivered to the person to whom the notice is given, or at the time
the notice is delivered to a common carrier for transmission or is actually
transmitted by the person giving the notice by electronic means to the person to
whom notice is given, whichever first occurs. Notice shall be given to the
parties hereto at the following addresses or to such other persons or addresses
as may be designated in writing by the party to receive such notice as any party
hereto shall hereafter specify to the other parties hereto.


<TABLE>
<CAPTION>
Name                                           Address
----                                           -------
<S>                                            <C>
Newhall Management Corporation                 23823 Valencia Boulevard
                                               Valencia, CA 91355

George L. Argyros                              Arnel & Affiliates
                                               949 South Coast Drive, Suite 600
                                               Costa Mesa, CA 92626

Gary M. Cusumano                               The Newhall Land and Farming Company 23823
                                               Valencia Boulevard
                                               Valencia, CA 91355

Thomas L. Lee                                  The Newhall Land and Farming Company 23823
                                               Valencia Boulevard
                                               Valencia, CA 91355

Thomas V. McKernan, Jr.                        Automobile Club of So. California
                                               3333 Fairview Road
                                               Costa Mesa, CA 92626

Henry K. Newhall                               118 Fernwood Drive
                                               San Rafael, CA 94901

Jane Newhall                                   2950 Pacific Avenue
                                               San Francisco, CA 94115

Peter T. Pope                                  Pope & Talbot, Inc.
                                               P.O. Box 8171
                                               Portland, OR 97207

Carl E. Reichardt                              Wells Fargo & Company
                                               P.O. Box 63710
                                               San Francisco, CA 94163

Thomas C. Sutton                               Pacific Life Insurance Company
                                               700 Newport Center Drive
                                               Newport Beach, CA 92660


                                       6
<PAGE>

Barry Lawson Williams                          Williams Pacific Ventures, Inc.
                                               109 Stevenson Street, 5th Floor
                                               San Francisco, CA 94105

Ezra K. Zilkha                                 Zilkha & Sons, Inc.
                                               767 Fifth Avenue, Suite 4605
                                               New York, NY 10153-0002

Newhall Management Corporation                 23823 Valencia Boulevard
Voting Trust                                   Valencia, CA 91355
</TABLE>

                                    ARTICLE 9

                                  MISCELLANEOUS

                  Section 9.1       SUCCESSORS AND ASSIGNS. Except as otherwise
herein provided, this Agreement shall bind and inure to the benefit of each and
all of the successors and assigns of the parties.

                  Section 9.2       AMENDMENT. This Agreement may be modified
only by a subsequent written agreement executed by all of the parties hereto,
except for the addition or termination of parties to this Agreement pursuant to
Sections 6.1 and 7.1(b).

                  Section 9.3       ENTIRE AGREEMENT. This Agreement and the
Voting Trust Agreement constitute the entire agreement between the parties and
supersede any and all prior agreements and understandings, both oral and
written, between and among the parties hereto.

                  Section 9.4       FURTHER ACTS. Each party to this Agreement
agrees to perform any further acts and execute and deliver any documents that
may be reasonably necessary or appropriate to carry out the provisions of this
Agreement.

                  Section 9.5       SEVERABILITY. If any provision of this
Agreement is held to be illegal, void, or unenforceable, the remaining
provisions will continue to be in full force and effect.

                  Section 9.6       GOVERNING LAW. This Agreement shall be
construed in accordance with and governed by the laws of the State of California
as applied to agreements solely among California residents to be executed and
performed entirely within California.

                  Section 9.7       COUNTERPARTS. This Agreement may be
executed in one or more counterparts, each of which shall be deemed an original,
but all of which together shall constitute one and the same instrument.

                  Section 9.8       GENDER; NUMBER.  The use of any gender shall
be construed to include any or all other genders where appropriate. The singular
shall include the plural, and vice versa.

                  Section 9.9       SECTION HEADINGS.  The section and other
headings are for reference only and shall not affect in any way the meaning or
interpretation of this Agreement.

                  Section 9.10      SPECIFIC PERFORMANCE. Each party
acknowledges that it has bargained for the performance of the specific duties
and obligations of each of the parties contained in this Agreement, and that, in
the event of a default by any party, money damages would be difficult to
determine and, in any event, would not adequately compensate the injured party
or parties. Accordingly, each party agrees and consents to the entry by a court
of competent jurisdiction of a judgment or decree of specific performance with
respect to its duties and obligations in the event of its failure to perform
such duties and obligations in accordance with the terms of this Agreement.


                                       7
<PAGE>

                  Section 9.11      SUBCHAPTER S ELECTION. The Shareholders
agree that it is in the best interests of each Shareholder (including his
Permitted Transferees) and the Company to elect to be taxed under Subchapter S
of the Code, and in furtherance thereof the Owners each agree to provide written
consents to the Subchapter S election whenever such consents are requested by
the Board of Directors of the Company.

                  Section 9.12      FILING. Upon execution of this Agreement, or
any amendment to this Agreement, and upon the addition of parties to this
Agreement pursuant to Section 6.1, a copy of the agreement or amendment shall be
filed in the principal executive office of the Company in the State of
California with the secretary and the copy shall be open to the inspection of
any shareholder of the Company during the normal business hours of the Company.

                  IN WITNESS WHEREOF, the parties have executed this Agreement
as of the day and year first set out above.

<TABLE>
<CAPTION>
                                            NEWHALL MANAGEMENT CORPORATION

<S>                                         <C>
          Number of Shares Owned            By:         /s/ Trude Tsujimoto
                                                     ---------------------------------
                                                     TRUDE A. TSUJIMOTO, Secretary

                    350                     By:         /s/ George L. Argyros
                                                     ---------------------------------
                                                     GEORGE L. ARGYROS

                    350                     By:         /s/ Gary M. Cusumano
                                                     ---------------------------------
                                                     GARY M. CUSUMANO

                    370                     By:         /s/ Thomas L. Lee
                                                     ---------------------------------
                                                     THOMAS L. LEE

                    350                     By:         /s/ Thomas V. McKernan, Jr.
                                                     ---------------------------------
                                                     THOMAS V. MCKERNAN, JR.

                    370                     By:         /s/ Henry K. Newhall
                                                     ---------------------------------
                                                     HENRY K. NEWHALL

                    20                      By:         /s/ Jane Newhall
                                                     ---------------------------------
                                                     JANE NEWHALL

                    350                     By:         /s/ Peter Pope
                                                     ---------------------------------
                                                     PETER T. POPE

                    370                     By:         /s/ Carl E. Reichardt
                                                     ---------------------------------
                                                     CARL E. REICHARDT

                    350                     By:         /s/ Thomas Sutton
                                                     ---------------------------------
                                                     THOMAS C. SUTTON

                    350                     By:         /s/ Barry Lawson Williams
                                                     ---------------------------------
                                                     BARRY LAWSON WILLIAMS


                                       8
<PAGE>

                    370                     By:         /s/ Ezra Zilkha
                                                     ---------------------------------
                                                     EZRA K. ZILKHA

                                            NEWHALL MANAGEMENT CORPORATION
                                            VOTING TRUST

                                            By:         /s/ Trude Tsujimoto
                                                     ---------------------------------
                                                     Trude A. Tsujimoto, Secretary of Newhall
                                                     Management Corporation, as Trustee
</TABLE>


                                       9
<PAGE>

                                    EXHIBIT A


                  THE TRANSFER OF THE SECURITIES REPRESENTED BY THIS
CERTIFICATE, THE VOTING RIGHTS OF THE HOLDER HEREOF AND CERTAIN OTHER RIGHTS OF
THE HOLDER HEREOF ARE SUBJECT TO AND RESTRICTED BY THE TERMS AND CONDITIONS OF
AN AMENDED AND RESTATED SHAREHOLDERS' AGREEMENT DATED AS OF JULY 19, 2000, A
VOTING TRUST AGREEMENT DATED AS OF NOVEMBER 14, 1990, AS AMENDED, AND THE BYLAWS
OF NEWHALL MANAGEMENT CORPORATION IN EACH CASE AS THE SAME MAY BE MODIFIED,
AMENDED OR SUPPLEMENTED FROM TIME TO TIME. NO TRANSFER OF THE SECURITIES
REPRESENTED HEREBY SHALL BE VALID OR EFFECTIVE UNLESS THE TERMS AND CONDITIONS
OF SAID AGREEMENTS, COPIES OF WHICH ARE ON FILE AT THE PRINCIPAL EXECUTIVE
OFFICE OF NEWHALL MANAGEMENT CORPORATION, IN THE STATE OF CALIFORNIA, HAVE BEEN
SATISFIED.


                                       10
<PAGE>

                                    EXHIBIT B
                         consent and agreement of spouse


                  The undersigned spouse of ______________________________ , a
shareholder of Newhall Management Corporation, formerly known as New Newhall
Management Corporation (the "Company"), who is a party to the Amended and
Restated Shareholders' Agreement ("Restated Shareholders' Agreement") dated as
of July 19, 2000, among Newhall Management Corporation, its shareholders and the
Newhall Management Corporation Voting Trust, which amends and restates in full
the Shareholders' Agreement dated as of November 14, 1990 by the parties
thereto, and to a Voting Trust Agreement dated as of November 14, 1990, as
amended, among Newhall Management Corporation, its shareholders and the trustee
of the Newhall Management Corporation Voting Trust, hereby acknowledges and
agrees that he or she:

                  1. Has read the Restated Shareholders' Agreement, the Voting
Trust Agreement and the Bylaws of the Company;

                  2. Has been informed of and is familiar with the background of
and the reasons for the provisions of the Restated Shareholders' Agreement,
Voting Trust Agreement and Bylaws of the Company;

                  3. Hereby consents to the terms and conditions of the Restated
Shareholders' Agreement, the Voting Trust Agreement and the Bylaws of the
Company as the same may be modified, amended or supplemented from time to time,
agrees to provide all notices and information required by him or her, and
confirms his or her express agreement to be bound by any required transfer which
shall arise in the event of the occurrence with respect to his or her spouse, of
any of the events set forth in said Restated Shareholders' Agreement or the
Bylaws of the Company which give rise to a required transfer, including divorce,
dissolution of marriage or separation, and to cooperate fully and take all such
action as may be necessary to facilitate the exercise of any required transfer
in accordance with the Restated Shareholders' Agreement, as it may be amended
from time to time; and

                  4. Hereby consents to any amendment to the Restated
Shareholders' Agreement, the Voting Trust Agreement and Bylaws of the Company
and to any change in the parties to the Restated Shareholders' Agreement and the
Voting Trust Agreement.

Dated as of _______________, 2000

                                              ----------------------------------


                                       11