The Supreme Court on Wednesday will consider the legality of President Donald Trump's decision to end Temporary Protected Status that potentially impacts millions of migrants. 

The program permits eligible migrants to live and work in the U.S. legally if they're unable to return to their home countries due to natural disasters, war or other temporary conditions. 

When it agreed to review the case, the high court took the unusual step of granting "certiorari before judgment," which means it reviews the merits of the case before federal appeals courts have reviewed district court rulings, Fox News reported. 

The Trump administration has tried to revoke the TPS designations for 13 countries since January. The court is expected to consider the power of the courts to review the designations, as opposed to the merits of the individual designations. 

A ruling in favor of the Trump administration could therefore impact as many as 1.3 million migrants living in the U.S. legally under the program.