Stephen Miller, President Trump's top policy adviser, said Friday the White House is exploring the option of suspending habeas corpus, the constitutional provision that protects from unlawful detainment.

A writ of habeas corpus requires authorities to produce in court an individual they are holding and justify their confinement. Article I of the Constitution says the "privilege of the writ of habeas corpus shall not be suspended, unless when in cases of rebellion or invasion the public safety may require it."

Stephen Miller, a top aide, repeated a justification used in the immigration crackdown: that the country is fighting an invasion. But it is unclear if the president has the power to take such a step.