I've recopied below Miss. Code Ann. Sec. 77-5-727. Subsection (u) appears to answer your question, at least as to purchases of electric power. I'm not aware of anything under the joint action agancy law that empowers the entity to buy gas on behalf of its members.

Section 77-5-729 provides authority for the member utility to contract with the joint agency to purchase power. It's recopied below as well.


? 77-5-725. Powers of joint agencies
Current through End of 2000 3rd Ex. Sess.
References     Annotations
Each joint agency shall have all of the rights and powers necessary or convenient to carry out and effectuate the purposes and provisions of this article, including, but without limiting the generality of the foregoing, the rights and powers:
(a) To adopt bylaws for the regulation of the affairs and the conduct of its business, and to prescribe rules, regulations and policies in connection with the performance of its functions and duties;
(b) To adopt an official seal and alter the same at pleasure;
(c) To maintain an office at such place or places as it may determine;
(d) To sue and be sued in its own name, and to plead and be impleaded;
(e) To receive, administer and comply with the conditions and requirements respecting any gift, grant or donation of any property or money;
(f) To acquire by purchase, lease, gift or otherwise, or to obtain options for the acquisition of, any property, real or personal, improved or unimproved, including an interest in land less than the fee thereof;
(g) To sell, lease, exchange, transfer or otherwise dispose of, or to grant options for any such purposes with respect to, any real or personal property or interest therein;
(h) To pledge or assign any money, rents, charges or other revenues and any proceeds derived by the joint agency from the sales of property, insurance or condemnation awards;
(i) To issue bonds of the joint agency for the purpose of providing funds for any of its corporate purposes;
(j) To study, plan, finance, construct, reconstruct, acquire, improve, enlarge, extend, better, own, operate and maintain, one or more projects, either individually or jointly, with one or more municipalities in this state or any other state owning electric distribution facilities or with any political subdivision, agencies or instrumentalities of any state, or with any one or more joint agencies created pursuant to this article, or any person, firm, association or corporation, public or private, engaged in the generation, transmission or distribution of electric power and energy within this state or any other state, and to pay all or any part of the costs thereof from the proceeds of bonds of the joint agency or from any other funds made available to the joint agency;
(k) To authorize the construction, operation or maintenance of any project or projects by any person, firm or corporation, including political subdivisions and agencies of any state, or of the United States;
(l) To acquire by lease, purchase or otherwise an existing project or a project under construction, or any interest therein, or portion thereof;
(m) With the unanimous consent of the member municipalities, to sell or otherwise dispose of any project or projects, or any interest therein or portion thereof.  The member municipalities may enter into an agreement with the joint agency whereby certain types of property may be traded or otherwise disposed of without unanimous consent of the member municipalities;
(n) To fix, charge and collect rents, rates, fees and charges for electric power or energy and other services, facilities and commodities sold, furnished or supplied through any project;
(o) To generate, produce, transmit, deliver, exchange, purchase or sell for resale only, electric power or energy, and to enter into contracts for any or all such purposes;
(p) To negotiate and enter into contracts for the purchase, sale, exchange, interchange, wheeling, pooling, transmission or use of electric power and energy with any municipality in this state or any other state owning electric distribution facilities, or with any political subdivisions, agencies or instrumentalities of any other state or with other joint agencies created pursuant to this article, any electric power association, any public or private utility, and any state, federal or municipal agency which owns electric generation, transmission or distribution facilities in this state or any other state;
(q) To make and execute contracts and other instruments necessary or convenient in the exercise of the powers and functions of the joint agency under this article, including contracts with persons, firms, corporations and others;
(r) To apply to the appropriate agencies of the state, the United States or any state thereof, and to any other proper agency for such permits, licenses, certificates or approvals as may be necessary, and to construct, maintain and operate projects in accordance with, and to obtain, hold and use, such licenses, permits, certificates or approvals in the same manner as any other person or operating unit of any other person;  provided, however, nothing herein contained shall be construed to require the joint agency to obtain any permit, license, certificate or approval from the Public Service Commission of Mississippi;
(s) To employ engineers, architects, attorneys, real estate counselors, appraisers, financial advisors and such other consultants and employees as may be required in the judgment of the joint agency and to fix and pay their compensation from funds available to the joint agency therefor;
(t) To purchase all kinds of insurance including, but not limited to, insurance against business interruption, and/or risks of damage to property;
(u) To purchase power and energy and related services from any source on behalf of its members and other customers and to sell the same to its members and other customers in such amounts, with such characteristics, for such periods of time and under such terms and conditions as the board of commissioners shall determine;  and
(v) To do all acts and things necessary, convenient or desirable to carry out the purposes, and to exercise the powers granted to the joint agency herein.


? 77-5-729. Contracts by members to buy power from joint agencies
Current through End of 2000 3rd Ex. Sess.
References
Any municipality which is a member of the joint agency may contract to buy from the joint agency power and energy required for its present or future requirements, including the capacity and output of one or more specified projects.  As the creation of a joint agency is an alternative method whereby a municipality may obtain the benefits and assume the responsibilities of ownership in a project, any such contract may provide that the municipality so contracting shall be obligated to make the payments required by the contract whether or not a project is completed, operable, operating, retired or decommissioned and notwithstanding the suspension, interruption, interference, reduction, curtailment or termination of the output of a project or the power and energy contracted for, and that such payments under the contract shall not be subject to any reduction whether by offset or otherwise, and shall not be conditioned upon the performance or nonperformance of the joint agency or any other member of the joint agency under the contract or any other instrument.  Any contract with respect to the sale or purchase of capacity or output of a project entered into between a joint agency and its member municipalities may also provide that if one or more of such municipalities shall default in the payment of its or their obligations, with respect to the purchase of said capacity or output, then in that event the remaining member municipalities which are purchasing capacity and output under the contract shall be required to accept and pay for and shall be entitled proportionately to and may use or otherwise dispose of the capacity or output which was to be purchased by the defaulting municipality.
Notwithstanding the provisions of any other law to the contrary, any such contracts with respect to the sale or purchase of capacity, output, power or energy from a project may extend for a period not exceeding fifty (50) years from the date a project is estimated to be placed in normal continuous operation;  and the execution and effectiveness thereof shall not be subject to any authorizations or approvals by the state or any agency, commission or instrumentality or political subdivision thereof except as in this article specifically required and provided.
Payments by a municipality under any contract for the purchase of capacity and output from a joint agency shall be made solely from the revenues derived from the ownership and operation of the electric system of said municipality and any obligation under such contract shall not constitute a legal or equitable pledge, charge, lien or encumbrance upon any property of the municipality or upon any of its income, receipts or revenues, except the revenues of its electric system, and neither the faith and credit nor the taxing power of the municipality are, or may be, pledged for the payment of any obligation under any such contract.  A municipality shall be obligated to fix, charge and collect rents, rates, fees and charges for electric power and energy and other services, facilities and commodities, sold, furnished or supplied through its electric system sufficient to provide revenues adequate to meet its obligations under any such contract and to pay any and all other amounts payable from or constituting a charge and lien upon such revenues, including amounts sufficient to pay the principal of and interest on bonds heretofore or hereafter issued by the municipality for purposes related to its electric system.
Any municipality which is a member of a joint agency may furnish the joint agency with money derived solely from the ownership and operation of its electric system or facilities and may make available for the use of the joint agency any personnel, equipment and property, both real and personal, which is a part of its electric system or facilities.
Any member of a joint agency may contract for, advance or contribute funds derived solely from the ownership and operation of its electric system or facilities to a joint agency as may be agreed upon by the joint agency and the member, and the joint agency shall repay such advances or contributions from proceeds of bonds, from operating revenues or from any other funds of the joint agency, together with interest thereon as may be agreed upon by the member and the joint agency.