Exhibit 5.1

May 3, 2007

Gran Tierra Energy, Inc.
300, 611-10^th Avenue S.W.
Calgary, Alberta T2R 0B2
Canada

Ladies and Gentlemen:

     We have acted as special Nevada corporate counsel for Gran Tierra Energy, Inc., a Nevada corporation (the “Company”), in connection with the sale by a certain stockholders of a total of 49,921,799 shares (the “Shares”) of Common Stock, $.001 par value and 24,525,604 shares of Common Stock issuable upon the exercise of warrants (the “Warrant Shares”). This opinion letter is submitted to you at your request in connection with the filing by the Company of a Registration Statement on Form SB-2 on Form S-1, No. 333-140171 (the “Registration Statement”) with the Securities and Exchange Commission with respect to such sale.

     In connection with this opinion letter, we have examined and relied upon copies of the following documents, together with such other documents as we deemed necessary or advisable to render the opinions herein expressed:

     i. The articles of incorporation and bylaws of the Company as are currently in effect.

     ii. A certificate of the Company as to certain factual matters, including adoption of certain resolutions of the board of directors.

     iii. The form of Securities Purchase Agreement pursuant to which the Shares were issued.

     iv. The form of warrants (the “Warrants”) pursuant to which the Warrant Shares will be issued.

     v. The Registration Rights Agreement dated June 20, 2006.

     In our examinations we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, and the conformity to original documents and completeness of all documents submitted to us as certified or photostatic, facsimile or electronic copies and the authenticity of the originals of such certified

Gran Tierra Energy, Inc.
May 3, 2007
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or copied documents. We have further assumed that the subscription agreement has been duly executed and delivered by the parties and is valid and legally binding on the parties, and that the Shares and Warrant Shares have been issued in accordance with its terms. As to certain matters expressed herein, we have relied upon and assumed the accuracy and completeness of certificates and reports of various state authorities and public officials and of the Company.

     We are admitted to the Bar of the State of Nevada, and in rendering our opinions hereinafter stated, we have relied on the applicable laws of the State of Nevada, as those laws presently exist and as they have been applied and interpreted by courts having jurisdiction within the State of Nevada. We are not members of the Bar of any state other than the State of Nevada, and, therefore, except for the laws of the State of Nevada, we express no opinion as to the laws of any other state, federal laws of the United States of America, or other jurisdiction.

     Based upon the foregoing and in reliance thereon and subject to the assumptions exceptions, qualifications and limitations set forth herein, we are of the opinion that:

The Shares have been duly authorized and are validly issued, fully paid and nonassessable.

The Warrant Shares have been duly authorized and upon exercise of the Warrants in accordance with the terms thereof, the Warrant Shares will be validly issued, fully paid and nonassesable.

     This opinion letter speaks as of its date. We disclaim any express or implied undertaking or obligation to advise of any subsequent change of law or fact (even though the change may affect the legal analysis or a legal conclusion in this opinion letter). This opinion letter is limited to the matters set forth herein, and no opinion may be inferred or implied beyond the matters expressly stated herein. We consent to the filing of this opinion letter as an exhibit to the Registration Statement and the reference to our firm under the heading “Legal Matters” in the prospectus forming part of the Registration Statement.

Sincerely,

Kummer Kaempfer Bonner Renshaw & Ferrario
 

/s/ Kummer Kaempfer