Texas didn't allow Bush to build the fence that Congress ordered built and funded in 2006 and Texas won't let Trump build a wall because much of the Texas border is the river. Any fence or wall cuts off the people of Texas, and their animals (COWS), from the river and free use of their water. The land right down to the water is owned by people who live there and farm or ranch there on most of the border. The river is also for fishing and boating, which a wall would block.
It would take eminent domain to take that land. And that is very unpopular in Texas and elsewhere in the West.
The cost of the land would be astronomical and the cost of the state and federal lawsuits would be very costly and would be tied up in court for many years.
IMO JD2
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. . . The Secure Fence Act of 2006 was passed by Congress and signed by President George W. Bush on October 26, 2006.
The government of Mexico and ministers of several Latin American countries have condemned the plans.[15] Rick Perry, governor of Texas, also expressed his opposition saying that instead of closing the border it should be opened more and through technology support legal and safe migration. . .
@ http://www.alipac.us/f12/what-happened-fence-306742/
http://www.alipac.us/f12/tx-tpwd-rej...uction-118851/
http://www.alipac.us/f12/tx-governme...native-121481/
http://www.alipac.us/f12/tx-supreme-...-fence-150842/
. . . "As a result of the Secure Fence Act passed in 2006, the government built some 650 miles of fence along the 1,954-mile US-Mexico boundary. While 1,254 miles of that border is in Texas, the state has only some 100 miles of fence. . .
@ http://www.alipac.us/f12/keeping-fen...atchin-332522/