In recent days, Donald Trump has repeatedly threatened to declare a national emergency over the US-Mexico border wall.
The US President is seeking $US5.7 billion ($A8 million) from Congress to fund the wall, but the Democrats are refusing to budge.
As the federal government enters its third week of a partial shutdown, Mr Trump’s threat to invoke emergency powers still stands.
But what exactly does this mean?
WHAT IS A NATIONAL EMERGENCY?
A national emergency is called in the case of a crisis — typically one that threatens national security.
Under the Constitution, decisions about spending taxpayer funds and creating policy are typically made by Congress.
But the National Emergencies Act of 1976 allows a president to bypass Congress and redirect funds in the event of a national emergency. The National Emergencies Act does not define “emergency,” giving the president broad discretion to declare one, legal experts have said.
The law empowers Congress to override an emergency declaration, but that requires action by both chambers, which would be hard to get since the Senate is run by Mr Trump’s fellow Republicans and the House of Representatives by Democrats.
By declaring a national emergency, the President “may seize property, organise and control the means of production, seize commodities, assign military forces abroad, institute martial law, seize and control all transportation and communication, regulate the operation of private enterprise, restrict travel, and, in a variety of ways, control the lives of United States citizens,” according to a 2007 Congressional Research Service report.
Congress has made a wide range of special powers available to a president who declares a national emergency.
One law allows the leader to redirect US Department of Defence construction funds that have not yet been allocated.
Another enables the US Army to halt civil projects and instead apply the funds and personnel to projects “essential to the national defence”.
HAS A NATIONAL EMERGENCY EVER BEEN DECLARED?
Yep — there’s actually 30 national emergencies currently in effect.
The first national emergency was called in 1979 by Jimmy Carter in response to the Iran hostage crisis, with an order blocking Iranian government property from entering the US.
George W Bush declared a national emergency following the September 11 terror attacks, and Barack Obama declared one in 2009 following a swine flu outbreak.
That said, this is the first national emergency consideration centred around a border wall.
OK, SO HOW WOULD TRUMP USE NATIONAL EMERGENCY POWERS?
Mr Trump has threatened to declare a national emergency in order to build a wall stretching along the US-Mexico border.
So far, the President and the Democrats are failing to see eye-to-eye on this, with meetings over the past week marred by tensions.
The standoff has seen a partial government shutdown that’s now spanned more than three weeks, leaving more than 800,000 federal workers without pay or being put on unpaid leave.
Mr Trump argues that the wall is needed to keep illegal immigrants out of the country.
In a prime-time address to the nation on Wednesday, he said illegal migrants strained public resources, drove down jobs and wages, and served as a “pipeline for vast quantities of illegal drugs”.
The Democrats in turn have argued the wall is a waste of money, accusing Mr Trump of fearmongering and misleading the public.
WOULD DECLARING A NATIONAL EMERGENCY WORK?
Possibly — but there would be major hurdles.
A practical issue for Mr Trump, even if he could credibly argue that an emergency exists, is that he would need to get his wall money out of whatever funds are left over from a pool of about $US10.4 billion ($A14.5 billion) in military construction projects during the current fiscal year, which ends on September 30.
The US military has not disclosed how much funding might be left over in its military construction budget. It was unclear whether any cash still available would be enough to make significant headway in building the border wall.
House Armed Services Committee Chairman Adam Smith said that, while Mr Trump does have the authority to call a national emergency, it would be “wide open” to facing a court challenge.
“In this case, I think the President would be wide open to a court challenge saying, ‘Where is the emergency?’” he told ABC News. “You have to establish that in order to do this. But beyond that, this would be a terrible use of Department of Defence dollars.
“I don’t think you should use the military to advance your agenda,” he said.