U.S. Vice President Mike Pence reiterated Monday that the White House is looking into whether President Donald Trump can declare a national emergency at the U.S.-Mexico border that would allow him to order the military to build a wall.

that he will give a speech Tuesday at 9 p.m. ET 鈥渙n the Humanitarian and National Security crisis on our Southern Border.鈥 Some are speculating he will declare a national emergency in the speech.

鈥 Watch: Explaining Trump's border wall

But Yale Law Professor Bruce Ackerman tells 麻豆影视 Channel that there is no legal way for Trump to use such a decree to build his border wall.

Ackerman points to a U.S. Supreme Court case decided when President Harry Truman nationalized steel mills and ordered all striking employees back to work during the Korean War, in violation of federal law.

鈥淭he Supreme Court holds that this is unconstitutional to use the Commander in Chief power to violate federal domestic law,鈥 according to Ackerman. 鈥淭hat is precisely what President Trump is proposing to do.鈥

that states: 鈥淲hoever, except in cases and under circumstances expressly authorized by the Constitution or Act of Congress, willfully uses any part of the Army or the Air Force ... to execute the laws shall be fined under this title or imprisoned not more than two years, or both.鈥

鈥淭his means that, immediately, members of the army are going to have to make a hard choice,鈥 says Ackerman. 鈥淪hould they obey the president and commit a criminal offence or should they uphold the rule of law and disobey the president?鈥

鈥淭his is a tragedy,鈥 Ackerman went on. 鈥淭he crisis of this kind in which the military has to decide whether it鈥檚 going to uphold the law or obey the president is precisely the scenario that has led many Latin American countries to military coups for the last 150 years.鈥

鈥淲orse yet, he鈥檚 violating the Constitution in a way that requires each military man to decide whether he鈥檚 going to obey the Constitution as he is sworn to do in his oath or the president of the United States,鈥 Ackerman added.

Earlier this week, Ackerman outlined a number of reasons in an about why he鈥檚 certain Trump can鈥檛 legally order the military to build his wall by declaring a national emergency.

In addition to it not being constitutional and violating the 1956 statute, he writes that it鈥檚 鈥減ossible to imagine a situation in which the president might take advantage of the most recent exception, enacted in 2011, which authorized the military detention of suspected terrorists associated with Al Qaeda or the Taliban,鈥 but goes on to say that would be 鈥渦nconscionable.鈥

Trump did claim on Friday that there are 鈥渢errorists coming through the southern border鈥 and White House Press Secretary Sarah Huckabee Sanders said on Fox News last week that 鈥渘early 4,000 known or suspected terrorists鈥 have come into the country illegally, mostly from Mexico. A State Department report issued in September found "no credible evidence indicating that international terrorist groups have established bases in Mexico, worked with Mexican drug cartels or sent operatives via Mexico into the United States."

With files from The Associated Press