EXHIBIT 5.1



                                 August 14, 2006


Structured Obligations Corporation
270 Park Avenue
New York, New York 10017


    Re:  Structured Obligations Corporation Registration Statement on Form S-3


Ladies and Gentlemen:

         At your request,  we have examined the  Registration  Statement on Form
S-3 filed by Structured  Obligations  Corporation,  a Delaware  corporation (the
"Registrant"),  with the Securities  and Exchange  Commission on the date hereof
(the  "Registration  Statement"),  in connection with the registration under the
Securities  Act of 1933, as amended (the "Act"),  of certain trust  certificates
(the  "Certificates").   The  Certificates  are  issuable  in  series  (each,  a
"Series").  Each Series of  Certificates  will be issued under a separate Series
Supplement  to  that  certain  Base  Trust  Agreement   (together,   the  "Trust
Agreement")  by  and  between  the  Registrant  and  a  trustee  named  therein,
establishing an individual trust for such Series (each, a "Trust").  Each Series
of Certificates is to be sold as set forth in the  Registration  Statement,  any
amendments  thereto,  and the prospectus and prospectus  supplement  relating to
such Series.

         We have examined such  instruments,  documents and records as we deemed
relevant and necessary as a basis of our opinion hereinafter expressed.  In such
examination,  we have assumed the following:  (a) the  authenticity  of original
documents  and the  genuineness  of all  signatures;  (b) the  conformity to the
originals  of all  documents  submitted  to us as  copies;  and (c)  the  truth,
accuracy and  completeness of the  information,  representations  and warranties
contained  in the  records,  documents,  instruments  and  certificates  we have
reviewed.

         Based  on  such  examination,  we are  of the  opinion  that  when  the
Certificates of each Series have been duly executed, authenticated and delivered
in accordance with the Trust  Agreement and sold in the manner  described in the
Registration Statement,  any amendment thereto and the prospectus and prospectus
supplement  relating  thereto,  the  Certificates of such Series will be legally
issued, fully paid, binding and non-assessable  obligations of the Trust created
by the Trust Agreement,  and the holders of the Certificates of such Series will
be entitled to the benefits of the Trust Agreement except as enforcement thereof
may  be   limited  by   applicable   bankruptcy,   insolvency,   reorganization,
arrangement,  fraudulent  conveyance,  moratorium,  or other laws relating to or
affecting the rights of creditors  generally  and general  principles of equity,
including without limitation concepts of materiality, reasonableness, good faith
and fair dealing,  and the possible  unavailability  of specific  performance or
injunctive relief,  regardless of whether such enforceability is considered in a
proceeding in equity or at law.

         We hereby  consent to the  filing of this  opinion as an exhibit to the
Registration  Statement  and to the use of our name  wherever  appearing  in the
Registration  Statement and each prospectus  contained  therein.  In giving such
consent,  we do not consider  that we are  "experts,"  within the meaning of the
term as used in the Act or the  rules  and  regulations  of the  Securities  and
Exchange  Commission  issued  thereunder,  with  respect  to  any  part  of  the
Registration Statement, including this opinion as an exhibit or otherwise.


                                             Very truly yours,



                                             ORRICK, HERRINGTON & SUTCLIFFE LLP