Temporary Protected Status (TPS)
"The Secretary of Homeland Security may designate a foreign country for TPS due to conditions in the country that temporarily prevent the country's nationals from returning safely, or in certain circumstances, where the country is unable to handle the return of its nationals adequately."
"The government's site says 'TPS does not lead to permanent resident status,' and strictly speaking, that is correct; the attorney general can terminate it, at which point the people in question revert to their original status - i.e., in most cases go back to being illegal aliens. But in practice, TPS is renewed as many times as necessary to ensure that no one is deported. Only in the smallest of cases, involving a few dozen or at most a few hundred people, has this 'temporary' status actually been ended without everyone getting a green card, and as far as I know, no one has ever been made to leave because they lost TPS."