Much of the government has been shut down for more than 16 days because President Donald Trump insists that Congress fund a border wall that is both a terrible idea and illegal.

The shutdown is because Trump demands extending the existing border walls and barriers to vast areas that make no sense largely because they are in the Rio Grande floodplain. Building barriers in that floodplain was such a problematic idea that a 1970 treaty between United States and Mexico explicitly bans them.

[...]

The 1970 “Treaty to Resolve Pending Boundary Differences and Maintain the Rio Grande and Colorado River as the International Boundary” states that the joint U.S.-Mexico International Boundary and Water Commission (IBWC) “must approve construction of works proposed in either country” along those rivers. It explicitly prohibits the construction of projects “which, in the judgment of the commission, may cause deflection or obstruction of the normal flow of the river or of its flood flows.”

If Trump flagrantly violates the treaty to build his wall, not only will it lead to court challenges, but it will worsen relations with the very country we need to work with if the United States is to improve the border situation.