Among many other issues, that raises the question of where these families will be held as they await court hearings.

Family detention centers run by U.S. Immigration and Customs Enforcement have a current capacity of 3,335 beds, according to the latest federal budget allocations. But on average, 420 parents and kids are crossing the U.S.-Mexico border in family groups each day, according to U.S. Customs and Border Protection data obtained by NBC News.

At that rate, the family detention centers will be full within eight days — and an unknown number of those beds are already occupied.