Exhibit 5.1 Patton Boggs LLP 1660 Lincoln Street Suite 1900 Denver, Colorado 80264 (303) 830-1776 November 21, 2003 Double Eagle Petroleum Co. 777 Overland Trail (P.O. Box 766) Casper, Wyoming Gentlemen and Ladies: We have acted as counsel for Double Eagle Petroleum Co., a Maryland corporation (the "Company"), in connection with preparation of the Company's Registration Statement on Form S-3 (the "Registration Statement") under the Securities Act of 1933, as amended, concerning the registration of the transfer of up to 1,295,000 shares of the Company's $.10 par value common stock (the "Common Stock") by the selling shareholders named in the Registration Statement (the "Selling Stockholders"). We have examined such certificates, agreements, documents and papers, and we have made such other inquiries and investigations of law as we have deemed appropriate and necessary in order to express the opinion set forth in this letter. In our examinations, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, photostatic, or conformed copies and the authenticity of the originals of all such latter documents. In addition, as to certain matters we have relied upon certificates and advice from various state authorities and public officials, and we have assumed the accuracy of the material and the factual matters contained herein. Subject to the foregoing and on the basis of the aforementioned examinations and investigations, it is our opinion that the 1,295,000 shares of Common Stock being transferred by the Selling Stockholders as described in the Registration Statement have been legally issued and constitute fully paid and non-assessable shares of the Company's Common Stock. We hereby consent (a) to be named in the Registration Statement and in the prospectus that constitutes a part of the Registration Statement as acting as counsel in connection with the transfer of the Common Stock, including with respect to the validity of the Common Stock offered; and (b) to the filing of this opinion as an exhibit to the Registration Statement. This opinion is to be used solely for the purpose of the registration of the Common Stock and may not be used for any other purpose. Very truly yours, /s/ Patton Boggs LLP PATTON BOGGS LLP