The move will allow the US President to bypass Congress and divert government funds towards his much vaunted border wall.
The decision is drawing widespread criticism, with senior Democrats and Republicans accusing him of gross abuse of power.
Trump says the wall is needed to stop drugs, gangs and criminals entering America. But the number of undocumented migrants crossing the border is at a 20 year low. And the government's own data shows up to 90 percent of heroin, cocaine and methamphetamines is trafficked through official entry points.
Trump's declaration is already facing legal challenges. So could his apparent obsession with the wall push the United States towards a constitutional crisis?
And how would that affect the Trump administration?
Charles Moran, Republican Strategist & Trump Delegate 2016
Jeff Hauser, Executive Director, Revolving Door Project at the Center for Economic and Policy Research
Bruce Fein, a Political Analyst & former U.S. Associate Deputy Attorney General.