Under U.S. immigration law, a country such as El Salvador can accept someone deported from the U.S. who isn’t a citizen of that country if the person’s homeland refuses to accept them, says Theresa Cardinal Brown, a former homeland security official under the administrations of Presidents George W. Bush and Barack Obama.

The Trump administration is assessing whether it could take up El Salvador's offer to house U.S. citizens convicted of crimes in its jails, Secretary of State Marco Rubio said on Tuesday, despite the apparent illegality of such a move.

The Trump administration and the president of El Salvador said they struck a deal allowing the U.S. to ship detained migrants and imprisoned criminals to a mega-prison there