Tex. Const. art. XVI, § 21

All stationery, printing, fuel used in the legislature and departments of the government other than the judicial department, printing and binding of the laws, journals, and department reports, and all other printing and binding and the repairing and furnishing of the halls and rooms used during meetings of the legislature and in committees, except proclamations and such products and services as may be done by handicapped individuals employed in nonprofit rehabilitation facilities providing sheltered employment to the handicapped in Texas, shall be performed under contract, to be given to the lowest responsible bidder, below such maximum price and under such regulations as shall be prescribed by law. No member or officer of any department of the government shall in any way have a financial interest in such contracts, and all such contracts or programs involving the state use of the products and services of handicapped individuals shall be subject to such requirements as might be established by the legislature.