 Coffee sold through futures contracts may only be shipped to a New York Board of Trade-certified port, and Texas's ad valorem tax on warehouse inventories made it impossible for Houston to get such a certification.The tax was written into the Constitution of Texas, so the Greater Houston Coffee Association asked State Representative Joe E. Moreno and State Senator Mario Gallegos to present a constitutional amendment bill to exempt cocoa and coffee stored in Harris County warehouses from the tax.Voters approved the amendment in 2001.