President Donald Trump is still heavily considering a national emergency declaration as a means of paying for his border wall, and Senate Democrats are eager to make sure that doesn’t happen.

A group of Democratic lawmakers, led by Sens. Tom Udall and Martin Heinrich of New Mexico, are introducing a bill dubbed the RAIDER Act that would bar Trump from using money that has already been allocated to disaster relief and other military construction projects for the wall. The legislation is unlikely to see any movement in a Republican-controlled Senate, but it highlights just how opposed Democrats are to a potential emergency declaration.

We're introducing the RAIDER Act to stop the president from using a national emergency declaration to raid disaster relief funds for his border wall.

Congress is a co-equal branch of gov't. We can't let @POTUS go around us to build his wasteful wall. https://t.co/w9RCVyn77v — Tom Udall (@SenatorTomUdall) February 4, 2019

If Trump were to declare a national emergency, he could capitalize on the National Emergencies Act of 1976 to access as much as $35 billion in funding that’s been allocated to Military Construction and the US Army Corps of Engineers for various projects including natural disaster relief. The RAIDER Act seeks to prevent that.

Democrats have widely criticized any use of a national emergency declaration to access money for Trump’s wall. Such a move would be legally questionable, and, they argue, there is no national emergency at the border. As Democrats have repeatedly pointed out, the actual apprehensions of undocumented immigrants have dropped significantly in recent years. And many of the drugs that are transported into the US from Mexico are coming through official ports of entry.

“We must stand up and assert our role as a co-equal branch of government, and we must prevent the president from going around Congress to raid critical funds ... or a politically-motivated, unjustified national emergency declaration that isn’t based in reality,” Udall said in a statement.

If Trump does move forward with the declaration, Congress will still have an opportunity to stop him by passing a resolution rejecting the declaration, though the measure would require substantial Republican support. Because Trump would likely veto such a resolution, both chambers would need a two-thirds veto-proof majority to approve it. It’s unclear at this point if enough Republicans would band together with Democrats to make that happen.

A potential national emergency declaration is also expected to face a quick legal challenge, with House Democrats weighing a possible suit that would contest the president’s attempt to use federal funding without congressional support, according to the Washington Post. In a 2015 case, House Republicans used this same reasoning to argue that it was unconstitutional for the Obama administration to dole out federal funds to health insurers without congressional approval.

A little more than a week ago, Trump said he had “alternative” methods of obtaining wall money if a congressional committee convened to discuss border security did not reach an agreement that satisfied him.

Democrats, it seems, are more than prepared to mount their opposition.