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

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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]

 

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