The Senate’s top Democrats overseeing the Pentagon said Monday that President Donald Trump has no authority to divert defense funds to pay for construction of a wall along the border with Mexico, and that administration officials might put themselves in legal jeopardy if they were to do so.

Democratic Sens. Richard J. Durbin of Illinois and Jack Reed of Rhode Island outlined their analysis in a letter to Defense Secretary James Mattis. The senators requested that Mattis respond as to whether or not the Pentagon agrees.

“Based on a thorough review of appropriations law, the text of the Department of Defense Appropriations Act, 2018, and the 2006 and 2008 appropriations made for the National Guard to conduct specific construction activities near the border, we conclude that the Department of Defense has no legal authority, with or without a reprogramming request, to use appropriated funds for the construction of a border wall,” Durbin and Reed wrote in the Monday letter.

In general, the ranking members on both the Defense Appropriations Subcommittee and the Armed Services Committee have the ability to stop reprogramming requests, as current Armed Services Chairman John McCain of Arizona did during part of the administration of President Barack Obama.

But Durbin and Reed went a step further Monday, saying that not even a request to Congress could be sufficient given the particular legislative history of border security funding. They write that the Trump administration would risk running afoul of the Antideficiency Act.

That law bars the expenditure of federal funds for purposes for which money was not appropriated by Congress.

Trump had suggested moving funds from the Pentagon budget, which ballooned thanks to the 2018 omnibus spending measure he recently signed into law, to pay for the wall effort (which presumably would fall under the Department of Homeland Security budget).

“Such a controversial move could only be funded by cutting other vital priorities for our service members, mere weeks after the Department communicated its needs to the Senate Defense Appropriations Subcommittee during omnibus appropriation negotiations,” the Democrats wrote. “We request your views on the legal authority of the Department to use funds appropriated for specific purposes in the Department of Defense Appropriations Act, 2018, for such a construction project.”