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.

President Bukele, who labels himself as the "coolest dictator" and a "philosopher king," has built election success and immense popularity on an extreme security policy to combat gang violence in El Salvador, incarcerating large quantities of alleged gang members and securing a massive drop in homicides.

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.