Human rights groups have accused U.S. authorities of using Guantánamo Bay for decades to detain migrants fleeing Haiti, Cuba and other Caribbean nations.

President Donald Trump, who made the deportation of immigrants a central part of his campaign and presidency, said Wednesday that the U.S. will use a detention center at Guantánamo Bay, Cuba, to hold tens of thousands of the “worst criminal aliens.

The president has instructed officials to “begin preparing” a 30,000-person “migrant facility” at Guantánamo Bay. The list of concerns is not short.