Democratic leader Sen. Chuck Schumer says any effort by President Donald Trump to use military funding to build his border wall be blocked by lawsuits, according to the Washington Post.

The Washington Post reported that Trump is pushing military officials to shift a very small portion of their $700 billion 2018 budget to build up border defenses, and quoted Schumer saying:

This would be a blatant misuse of military funds and tied up in court for years. [Defense] Secretary Mattis ought not bother and instead use the money to help our troops, rather than advance the president’s political fantasies.

Schumer’s threat came after he worked with GOP leaders to allocate only $641 million for the construction of new border fences in the 2018 omnibus bill. The bill also includes language which bars Trump from spending money on the concrete-and-metal prototype walls which he touted in early March. According to the Post:

Trump, who told advisers he was spurned in a large spending bill last week when lawmakers only appropriated $1.6 billion for the border wall, has begun suggesting the Pentagon could fund the sprawling construction, citing a “national security” risk. After floating the notion to several advisers last week, he told Speaker Paul D. Ryan (R-Wis.) that the military should pay for the wall in a meeting last Wednesday in the White House residence, according to three people familiar with the meeting. Ryan offered little reaction to the notion, these people said, but senior Capitol Hill officials later said it was an unlikely prospect.

Long-standing laws sharply restrict what “reprogramming” Presidents can do with appropriated funds. For example, President must spend most of the funds allocated by Congress, and can only shift a small percentage of each program’s funds to another program.

However, Trump is also the Commander in Chief of the military, and he has begun arguing that border defenses are a national security need which falls outside Congress’ direct control. On March 25, for example, he argued that the wall should be built by the military, dubbed “M”

Because of the $700 & $716 Billion Dollars gotten to rebuild our Military, many jobs are created and our Military is again rich. Building a great Border Wall, with drugs (poison) and enemy combatants pouring into our Country, is all about National Defense. Build WALL through M! — Donald J. Trump (@realDonaldTrump) March 25, 2018

Trump’s push to enlist the military in his wall-building plans are likely to be resisted by Defense Secretary Jame Mattis, who has successfully avoided most partisan disputes. Also, Pentagon leaders do not want to divert troops and funding to a police-style mission on the border.

Former Sen. Jeff Sessions, now the Attorney General, may also oppose the reprogramming effort, in part, because he spent much time trying to block former President Barack Obama from evading Congress’ controls, such as Obama’s attempted 2012 ‘DACA’ amnesty.

But any dispute with Washington may help Trump show his political distance from Washington D.C., especially after D.C. insiders united to block his immigration reforms in the February Senate debate and in the March omnibus spending plan.