Exhibit
10.1


EXECUTION
COPY


INVESTOR
AGREEMENT


THIS INVESTOR AGREEMENT
(this “Agreement”) made and entered into this 20th day of July 2007, by
and between Électricité de France International, SA, a French
société anonyme (“EDFI”),
and Constellation Energy Group, Inc., a Maryland corporation (“Constellation”);


W I T N E
S S E T H:


WHEREAS, EDFI and
Constellation have been engaged in discussions relating to their respective
businesses;


WHEREAS, as a condition
to such discussions, an affiliate of EDFI and Constellation entered into a
non-disclosure agreement, dated as of February 26, 2007 (the “Nondisclosure
Agreement”);


WHEREAS, in connection
with such discussions, EDFI and Constellation, through their respective
affiliates, are concurrently entering into a joint venture to participate in
the development, ownership and operation of new nuclear projects in the United
States and Canada and related activities (the “Joint Venture”);


WHEREAS, also in
connection with such discussions, EDFI has proposed that it may acquire
beneficial ownership of outstanding shares of Constellation common stock,
without par value (the “Constellation Stock”); and


WHEREAS, EDFI and
Constellation wish to agree on the terms and conditions of such acquisition of
Constellation Stock as well as any related rights for EDFI.


NOW, THEREFORE, for and
in consideration of the rights and obligations contained herein, and for other
good and valuable consideration, the adequacy of which is hereby acknowledged,
it is covenanted and agreed as follows:


ARTICLE I

REPRESENTATIONS


Section 1.1             Representations of Constellation.  Constellation hereby represents and warrants
to EDFI as follows:


(a)           Constellation has all necessary
corporate power and authority to execute and deliver this Agreement and to
perform its obligations hereunder.  The
execution, delivery and performance of this Agreement by Constellation have
been duly and validly authorized by all necessary corporate action of
Constellation, and no other corporate proceedings on the part of Constellation
are necessary to authorize this Agreement or the performance by Constellation
of its obligations hereunder.


(b)           This Agreement has been duly and
validly executed and delivered by Constellation and, assuming the due
authorization, execution and delivery hereof by EDFI, constitutes a legal,
valid and binding obligation of Constellation enforceable against 













Constellation in accordance
with its terms, subject to the effects of bankruptcy, insolvency, fraudulent
conveyance, reorganization, moratorium and other similar laws relating to or
affecting creditors’ rights generally, general equitable principles (whether
considered in a proceeding in equity or at law) and any implied covenant of
good faith and fair dealing.


(c)           The execution, delivery and
performance of this Agreement by Constellation do not and will not conflict
with or violate (i) the articles of incorporation or bylaws of
Constellation, or (ii) any law, ordinance, rule, or regulation applicable
to Constellation.


Section
1.2             Representations of EDFI.  EDFI hereby represents and warrants to
Constellation as follows:


(a)           EDFI has all necessary corporate
power and authority to execute and deliver this Agreement and to perform its
obligations hereunder.  The execution,
delivery and performance of this Agreement by EDFI have been duly and validly
authorized by all necessary corporate action of EDFI, and no other corporate
proceedings on the part of EDFI are necessary to authorize this Agreement or
the performance by EDFI of its obligations hereunder.


(b)           This Agreement has been duly and
validly executed and delivered by EDFI and, assuming the due authorization,
execution and delivery hereof by Constellation, constitutes a legal, valid and
binding obligation of EDFI enforceable against EDFI in accordance with its
terms, subject to the effects of bankruptcy, insolvency, fraudulent conveyance,
reorganization, moratorium and other similar laws relating to or affecting
creditors’ rights generally, general equitable principles (whether considered
in a proceeding in equity or at law) and any implied covenant of good faith and
fair dealing.


(c)           The execution, delivery and
performance of this Agreement by EDFI do not and will not conflict with or
violate (i) the governing documents of EDFI, or (ii) any law,
ordinance, rule, or regulation applicable to EDFI.


(d)           EDFI, each of its subsidiaries and,
to the best of its knowledge, each of its controlled affiliates (EDFI, its
subsidiaries and controlled affiliates, collectively, the “EDFI Group”)
currently are not beneficial owners (determined as hereinafter provided) of any
Constellation Stock; provided, however, this representation shall
not apply to any investments made or managed by outside asset managers with
EDFI funds relating to contingent nuclear liabilities, whether such investments
have previously been made or are made in the future (any such investments
whenever made are hereinafter referred to as, “Permitted EDFI Investments”).
EDFI has no control over the funds used by the asset managers to make
Permitted EDFI Investments.   For
purposes of this Agreement, “controlled affiliate” shall mean any entity for
which EDFI Group would have the ability to direct the acquisition, disposition
or voting of Constellation Stock.



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ARTICLE
II

ACQUISITIONS AND DISPOSITIONS OF CONSTELLATION STOCK


Section 2.1             Acquisition of Constellation
Stock.  Until the expiration of the Term (as that term is defined herein) of the Agreement,
EDFI or any member of the EDFI Group shall be permitted to acquire and hold
shares of Constellation Stock as follows:


(a)           prior to the first anniversary of the
date of this Agreement, beneficial ownership, in the aggregate, of no more than
5.0% of the issued and outstanding shares of Constellation Stock;


(b)           from and after the first anniversary
of the date of this Agreement, beneficial ownership, in the aggregate, of no
more than 9.9% of the issued and outstanding shares of Constellation Stock;


provided, that (i) all such purchases made under this
Section 2.1 shall be done in such a manner as is consistent with then current
professional practices for the acquisition of shares of public companies, and
(ii) if after
the date of the execution of this Agreement EDFI acquires a subsidiary or
controlled affiliate which owns Constellation Stock, EDFI shall have sixty days
to divest such Constellation Stock (and during such sixty-day period (i) such
Constellation Stock shall not be included in any calculations under this
Section 2.1 and (ii) such sales shall not be subject to the limitations set
forth in Section 2.3).


Section
2.2             Standstill.  Until the expiration of the Term of this
Agreement, without
the prior written consent of Constellation, EDFI shall not, and shall cause
each member of the EDFI Group not to, singly or as part of a group, directly or
indirectly:


(a)           acquire or propose to acquire (other
than as a result of a stock split, stock dividend or other recapitalization of
Constellation) beneficial ownership of any equity securities of Constellation (“Equity
Securities”) or any rights to directly or indirectly acquire any Equity
Securities, except as contemplated by Section 2.1;


(b)           participate in any solicitation of
proxies or become a participant in any election contest with respect to
Constellation;


(c)           seek, or offer or make any proposal
to Constellation, its representatives or any shareholder of Constellation, or
otherwise make any public announcement with respect to, (1) any merger,
consolidation or sale of all or substantially all of the assets, or a majority
of the outstanding shares of Constellation Stock, or any other form of business
combination involving Constellation, (2) any form of restructuring,
recapitalization, liquidation or similar transaction involving Constellation,
or (3) any proposal or other statement inconsistent with the terms of this
Section 2.2, except as specifically contemplated by the terms of this Agreement
or the agreements governing the Joint Venture;


(d)           join with any other parties to form a
“group” with respect to Constellation Stock, as determined pursuant to Section
13(d) of the U.S. Securities Exchange Act of 1934, as amended;



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(e)           otherwise act, alone or in concert
with others, to seek or offer to control or influence, in any manner, the
management, board of directors or policies of Constellation, except as
otherwise contemplated by the terms of this Agreement or the agreements
governing the Joint Venture; or


(f)            enter into any agreement, disclose
any intention or knowingly advise, assist or encourage any other person to do
any of the above.


Notwithstanding anything
to the contrary in this Agreement, EDFI or any other member of the EDFI Group
may participate in any tender or exchange offer for Constellation Stock as a
seller or, subject to Section 3.2, vote any securities owned by it at any
special meeting of the holders of Constellation Stock to consider any such
business combination transaction.


Section 2.3             Dispositions of Constellation
Stock.  During the Term of this
Agreement, EDFI shall provide Constellation with three business days’ prior
written notice of its intention to sell any shares of Constellation Stock,
which notice shall include EDFI’s then good faith estimate of the approximate
number of shares of Constellation Stock proposed to be sold.  Subject to the limitations set forth below,
EDFI shall not be restricted in the actual number of shares it may sell
following the delivery of such notice regardless of the number of shares
intended to be sold as set forth in such notice.  Also during the Term of this Agreement, EDFI
shall (and shall cause each member of the EDFI Group to) only sell
Constellation Stock in a manner that does not disrupt the market for
Constellation Stock and in any event in accordance with the limits set forth
below:


(a)           until three years after the date of
this Agreement, EDFI shall not (and shall cause each member of the EDFI Group
not to) dispose of any shares of Constellation Stock, provided, that
this restriction shall no longer apply from and after (i) such time as a
majority of the members of the Constellation board of directors are not
directors nominated by a majority of the then-existing board members, or
(ii) the actual dissolution of the Joint Venture as a result of a deadlock
between the parties thereto, and


(b)           with respect to any sales of
Constellation Stock, the amount of Constellation Stock sold by the EDFI Group,
in the aggregate, shall not exceed, in any single day, twenty percent (20%) of
the average daily trading volume of Constellation Stock over the preceding
30-trading day period (other than transfers to affiliates who are bound by the
terms and conditions of this Agreement).


Section 2.4             Beneficial Ownership.  For purposes of this Agreement, “beneficial
ownership” shall be determined in accordance with Rule 13d-3 under the U.S.
Securities Exchange Act of 1934, as amended.


Section 2.5             Constellation Issuances.  If Constellation elects to consummate a
strategic transaction, alliance or investment that is within a framework
mutually developed by Constellation and EDFI, prior to such transaction,
alliance or investment Constellation and EDFI may agree that all or a portion
of  the funding for such transaction,
alliance or investment will be made by the issuance of Constellation securities
to a member of the EDFI Group in a form and containing terms and conditions to
be mutually agreed upon, which agreement the parties acknowledge may entail
amendments to this Agreement.



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ARTICLE
III

OBSERVER; VOTING; COMMERCIALLY REASONABLE EFFORTS


Section 3.1             Observer on Nuclear Committee.  For so long as each of EDFI (or any of its
affiliates or subsidiaries) and Constellation (or any of its affiliates or
subsidiaries) owns any membership interests in the Joint Venture, EDFI shall be
permitted to designate an observer to attend meetings of Constellation’s
Committee on Nuclear Power, provided, that such observer shall not be
permitted to attend any portion of a Committee on Nuclear Power meeting at
which the presence of such EDFI designated observer would contravene any
governmental law, regulation or clearance requirement.


Section
3.2             Voting of Constellation
Stock.  On any matters submitted to
the holders of Constellation Stock, EDFI shall (and shall cause each member of the EDFI Group to) vote any shares of Constellation Stock that
it beneficially owns in the manner recommended by the Constellation board of directors.


Section
3.3             Cooperation.  Constellation and EDFI each agree to use all
commercially reasonable efforts to facilitate the consummation of the
transactions contemplated hereby, including, without limitation, by taking
necessary actions to obtain antitrust approvals and facilitating obtaining any
necessary clearances so that an EDFI designee can attend all Committee on
Nuclear Power meetings.


ARTICLE
IV

MISCELLANEOUS


Section 4.1             Effectiveness.  This Agreement shall not become
effective until the last to occur of the following events:


(a)           the effectiveness of the Operating
Agreement of UniStar Nuclear Energy, LLC, dated as of the date hereof (the “Operating
Agreement”); and


(b)           all regulatory approvals required
from governmental authorities (including the expiration or termination of any
applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements
Act of 1976) shall have been obtained or concluded or, in the case of waiting
or suspense periods, expired or terminated;


provided, however, that this Agreement
shall terminate without further effect or obligation on the part of either
party if any of the above events has not occurred by September 30, 2007, except
in the case of clause (b) if the parties are working in good faith to obtain
any such outstanding regulatory approval(s) and such date has been extended by
written agreement of the parties.


Section 4.2             Term.  The term (the “Term”) of this
Agreement shall begin on the date hereof and continue until five years after
the date hereof.  Sections 2.1, 2.2, 2.3
and 3.2 shall be of no further force or effect following a change of control of
Constellation



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Section
4.3             Governing Law.  This Agreement shall be governed by, and construed in
accordance with, the laws of the State of New York.


Section 4.4             Dispute Resolution.


(a)           All disputes arising
out of or in connection with the present contract shall be finally settled
under the Rules of Arbitration of the International Chamber of Commerce by
three arbitrators.  The disputing
Member(s) and/or the Company shall each appoint one arbitrator, and those two
arbitrators shall then appoint a third arbitrator. The place of arbitration
shall be New York.  The language of the
arbitration shall be English.  The
arbitral tribunal shall render a reasoned award within six months from the date
of signature of the terms of reference. 
Any party to this contract shall have the right to have recourse to and
shall be bound by the Pre-arbitral Referee Procedure of the International
Chamber of Commerce in accordance with its Rules for a Pre-Arbitral Referee
Procedure.


(b)           Any decision or award
of the arbitral tribunal shall be final and binding upon the parties to the
arbitration proceeding.  The parties
hereto hereby waive to the extent permitted by applicable law any rights to
appeal or to review of such award by any court or tribunal.  The parties hereto agree that the arbitral
award may be enforced against the parties to the arbitration proceeding or
their assets wherever they may be found and that a judgment upon the arbitral
award may be entered in any court having jurisdiction thereof.


(c)           Each party acknowledges that the
other would not have an adequate remedy for money damages in the event that any
or all of the covenants contained in this Agreement were not performed in
accordance with their terms and therefore agrees that the other party shall be
entitled to other relief, including injunctive relief and specific performance
of such covenants, in addition to any other remedy to which such party may be
entitled.  Notwithstanding any other
provision of this Section 4.4, EDFI and Constellation shall have the right to
obtain injunctive relief from any federal or state court located in the Borough
of Manhattan, City of New York.  Each of
EDFI and Constellation hereby irrevocably consents to personal jurisdiction in
any such action and to service of process by mail in any manner permitted by
the laws of the State of New York and agrees that service of process by
registered mail sent to its principal executive office shall be effective
service of process for such action, suit or proceeding brought against such
party in any such court, and waives any objection to venue in any such New York
court.


Section 4.5             Successors and Assigns.  This Agreement shall inure to the benefit of
and be binding upon Constellation and EDFI and their respective affiliates,
successors and assigns, including any successor to Constellation or EDFI of
substantially all of Constellation’s or EDFI’s assets or business.


Section
4.6             Entire Agreement; Amendment.  This Agreement shall constitute the entire agreement
between the parties with regard to the subject matter hereof, provided,
that nothing in this Agreement is intended to amend or modify in any respect
the terms and conditions of the Nondisclosure Agreement or the Operating Agreement, and each shall
continue in full force and effect in accordance with its terms.  No modification, amendment or waiver of this
Agreement shall be binding without the written consent of the parties hereto.



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Section
4.7             Waiver.  It is understood and agreed that no failure
or delay in exercising any right, power or privilege hereunder shall operate as
a waiver thereof, nor shall any single or partial exercise thereof preclude any
further exercise thereof or the exercise of any other right, power or privilege
hereunder.


Section
4.8             Counterparts.  This Agreement may be executed in
counterparts, each of which shall be deemed to be an original, but both of
which shall constitute the same agreement.


Section 4.9             Other Agreements.   In the event (a) Constellation enters
into a similar agreement with a strategic, industrial shareholder who owns at
least 5 percent of the issued and outstanding Constellation Stock,
(b) such agreement is on terms which are materially more favorable to such
shareholder than the terms of this Agreement are to EDFI, and
(c) Constellation does not agree to amend this Agreement to provide EDFI
with the same terms and conditions, then EDFI shall no longer be subject to the
sales limitation set forth in Section 2.3(a).


[Signature page
follows.]



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IN WITNESS
WHEREOF, the parties have caused this Agreement to be executed by their
respective duly authorized officers as of the date first above written.


CONSTELLATION ENERGY GROUP, INC.


By:          /s/
Michael J. Wallace                                         

Name:  Michael J. Wallace

Title:  Executive Vice President


ÉLECTRICITÉ DE FRANCE
INTERNATIONAL, SA


By           /s/
J.L. Mathias                                                     

Name:  J.L. Mathias

Title:  COO


 


 


[Signature Page to
Investor Agreement]