Exhibit 5.1

                                VINSON & ELKINS
                               ATTORNEYS AT LAW

                            VINSON & ELKINS L.L.P.
                             2300 FIRST CITY TOWER
                              1001 FANNIN STREET
                          HOUSTON, TEXAS  77002-6760
                           TELEPHONE (713) 758-2222
                              FAX (713) 758-2346

                                August 27, 2001


Plains All American Pipeline, L.P.
PAA Finance Corp.
Plains Marketing, L.P.
All American Pipeline, L.P.
Plains Marketing GP Inc.
Plains Marketing Canada LLC
Plains Marketing Canada, L.P.
PMC (Nova Scotia) Company
(See attached addresses)

Ladies and Gentlemen:

     We have acted as counsel for Plains All American Pipeline, L.P., a Delaware
limited partnership (the "Partnership"), with respect to certain legal matters
                          -----------
in connection with the registration by the Partnership under the Securities Act
of 1933, as amended (the "Securities Act"), of the offer and sale by the
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Partnership from time to time, pursuant to Rule 415 under the Securities Act, of

     (1)  common units representing limited partner interests in the Partnership
          (the "Units");
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     (2)  debt securities, which may be co-issued by PAA Finance Corp., a
          Delaware corporation ("PAA Finance"), in one or more series,
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          consisting of notes, debentures or other evidences of indebtedness
          (the "Debt Securities"); and
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     (3)  guarantees (the "Guarantees") of the Debt Securities by Plains
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          Marketing, L.P., a Delaware limited partnership ("Plains Marketing"),
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          All American Pipeline, L.P., a Texas limited partnership ("All
                                                                     ---
          American Pipeline"), Plains Marketing GP Inc., a Delaware corporation
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          ("Plains Marketing GP Inc."), Plains Marketing Canada LLC, a Delaware
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          limited liability company ("Plains Marketing Canada LLC"), Plains
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          Marketing Canada, L.P., a Canadian limited partnership ("Plains
                                                                   ------
          Marketing
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          Canada, L.P."), and PMC (Nova Scotia) Company, a Nova Scotia
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          unlimited liability company ("PMC Nova Scotia" and, together with
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          Plains Marketing, All American Pipeline, Plains Marketing GP Inc.,
          Plains Marketing Canada LLC and Plains Marketing Canada, L.P., the
          "Subsidiary Guarantors").  The Units, Debt Securities and Guarantees
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          are collectively referred to herein as the "Securities."  We have also
                                                      ----------
          participated in the preparation of the Prospectus (the "Prospectus")
                                                                  ----------
          contained in the Partnership's Registration Statement on Form S-3 (the
          "Registration Statement") to which this opinion is an exhibit.
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          Capitalized terms not defined herein shall have the meanings ascribed
          to them in the Prospectus.

     We have examined the Registration Statement, the Prospectus, the Third
Amended and Restated Agreement of Limited Partnership of the Partnership (the
"Partnership Agreement"), the Certificate of Limited Partnership of the
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Partnership (the "Certificate") filed with the Secretary of State of Delaware
                  -----------
pursuant to the Delaware Revised Uniform Limited Partnership Act in connection
with the formation of the Partnership, other formation documents and agreements
of limited partnership, as applicable, of PAA Finance and the Subsidiary
Guarantors and such other documents as we have deemed necessary or appropriate
for purposes of this opinion.  In addition, we have reviewed certain
certificates of officers of the general partner of the Partnership and of public
officials, and we have relied on such certificates with respect to certain
factual matters that we have not independently established.

     In connection with this opinion, we have assumed that

     (1)  the Registration Statement, and any amendments thereto (including
          post-effective amendments), will have become effective;

     (2)  a Prospectus Supplement will have been prepared and filed with the
          Commission describing the Securities offered thereby;

     (3)  all Securities will be issued and sold in compliance with applicable
          federal and state securities laws and in the manner stated in the
          Registration Statement and the appropriate Prospectus Supplement;

     (4)  a definitive purchase, underwriting or similar agreement with respect
          to any Securities offered will have been duly authorized and validly
          executed and delivered by the Partnership and the other parties
          thereto; and

     (5)  any Securities issuable upon conversion, exchange or exercise of any
          Security being offered will be duly authorized, created and, if
          appropriate, reserved for issuance upon such conversion, exchange or
          exercise.

     Based upon and subject to the foregoing, we are of the opinion that:

     (1)  With respect to the Units, when (i) the Partnership has taken all
          necessary action to approve the issuance of such Units, the terms of
          the offering therof and related matters and (ii) the Units have been
          issued and delivered in accordance with the terms of the applicable
          definitive purchase, underwriting or similar agreement


          approved by the Partnership upon payment of the consideration therefor
          provided for therein, then the Units will be validly issued, fully
          paid and non-assessable.

     (2)  With respect to the Debt Securities and the Guarantees, when (i) the
          applicable Indenture has been duly qualified under the Trust Indenture
          Act of 1939, as amended; (ii) the Partnership, PAA Finance and the
          Subsidiary Guarantors, as applicable, have taken all necessary action
          to approve the issuance and terms of such Debt Securities and
          Guarantees, the terms of the offering thereof and related matters; and
          (iii) such Debt Securities and Guarantees have been duly executed,
          authenticated, issued and delivered in accordance with the provisions
          of the applicable Indenture and the applicable definitive purchase,
          underwriting or similar agreement approved by the Partnership, PAA
          Finance and the Subsidiary Guarantors, as applicable, upon payment of
          the consideration therefor provided for therein, such Debt Securities
          and Guarantees will be legally issued and will constitute valid and
          legally binding obligations of the Partnership, PAA Finance and the
          Subsidiary Guarantors, as applicable, enforceable against the
          Partnership, PAA Finance and the Subsidiary Guarantors, as applicable,
          in accordance with their terms, except as such enforcement may be
          subject to any applicable bankruptcy, insolvency, reorganization,
          fraudulent conveyance or other law relating to or affecting creditors'
          rights generally and general principles of equity.

     The opinions expressed herein are qualified in the following respects:

     (1)  We have assumed, without independent verification, that the
          certificates for the Units will conform to the specimens thereof
          examined by us and will have been duly countersigned by a transfer
          agent and duly registered by a registrar of the Units.

     (2)  We have assumed that (i) each document submitted to us for review is
          accurate and complete, each such document that is an original is
          authentic, each such document that is a copy conforms to an authentic
          original and all signatures on each such document are genuine and (ii)
          each certificate from governmental officials reviewed by us is
          accurate, complete and authentic, and all official public records are
          accurate and complete.

     (3)  This opinion is limited in all respects to federal laws, the Delaware
          Revised Uniform Limited Partnership Act and the Constitution of the
          State of Delaware, as interpreted by the courts of the State of
          Delaware and of the United States.


     We hereby consent to the references to this firm under the caption "Legal
Matters" in the Prospectus and to the filing of this opinion as an Exhibit to
the Registration Statement.  By giving such consent, we do not admit that we are
within the category of persons whose consent is required under Section 7 of the
Securities Act or the rules and regulations of the Securities and Exchange
Commission issued thereunder.

                                    Very truly yours,


                                    /s/ Vinson & Elkins L.L.P.
                                    --------------------------
                                    Vinson & Elkins L.L.P.


                                   Addresses
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Plains All American Pipeline, L.P.
333 Clay Street
Suite 2900
Houston, Texas 77002
Phone: (713) 646-4100
Fax:   (713) 646-4572

PAA Finance Corp.
333 Clay Street
Suite 2900
Houston, Texas 77002
Phone: (713) 646-4100
Fax:   (713) 646-4572

Plains Marketing, L.P.
333 Clay Street
Suite 2900
Houston, Texas 77002
Phone: (713) 646-4100
Fax:   (713) 646-4572

All American Pipeline, L.P.
333 Clay Street
Suite 2900
Houston, Texas 77002
Phone: (713) 646-4100
Fax:   (713) 646-4572

Plains Marketing GP Inc.
333 Clay Street
Suite 2900
Houston, Texas 77002
Phone: (713) 646-4100
Fax:   (713) 646-4572

Plains Marketing Canada LLC
333 Clay Street
Suite 2900
Houston, Texas 77002
Phone: (713) 646-4100
Fax:   (713) 646-4572

Plains Marketing Canada, L.P.
1200 Bow Valley Square IV
250 6th Ave. SW
Calgary, Alberta T2P 3H7
Canada

PMC (Nova Scotia) Company
1959 Upper Water Street
Suite 800
Halifax, Nova Scotia B3J 2X2
Canada