President Barack Obama's efforts to shield millions of undocumented immigrants from deportation suffered a major setback at the US Supreme Court on Thursday.
Justices in the under-strength court were split 4-4 over Obama's bid to change immigration policy by executive action, thus leaving lower court rulings blocking the effort in place.
The court would normally have had nine members, making a tie less likely, but Justice Antonin Scalia died in February and the Senate has refused to vote on Obama's nominee to replace him.
The deadlock leaves Obama's immigration policy in limbo, like the 4 million undocumented immigrants who stood to be awarded US work permits under the politically controversial plan.
Frustrated by Congress' repeated failure to pass immigration reform, in November 2014 Obama issued a decree to allow migrants whose children are legally resident to apply for permits.
This would have shielded the families from deportation while the politically-charged issue of their status is determined, but the governors of 26 Republican-led states challenged the order.
Federal courts in Texas and Louisiana put the measure on hold and the case passed to the Supreme Court, which on Thursday remained split along partisan progressive-conservative lines.