Justin Amash - Trump's declaration of emergency is a violation of our constitutional system

Interesting and I get why Amash would posit himself in this way due to his libertarian bent but it does not appear that, however misguided this act may be, that it violates the constitution.

Under a distinct provision, the president, “without regard to any other provision of law,” may repurpose funds for military construction projects, which, while not authorized by Congress, he deems “necessary to support such use of the armed forces.”