In a case involving changes to birthright citizenship, the justices heard arguments on whether a single federal judge in a single district can block Trump administration policy across the country.

Shortly after Trump issued his executive order to limit birthright citizenship, federal judges in Maryland, Massachusetts and Washington state declared it unconstitutional and blocked its enforcement nationwide. In response, Trump’s lawyers asked the court to rein in the “epidemic” of nationwide orders handed by district judges.

The Supreme Court heard a blockbuster case on Thursday that impacts how challenging or easy it will be for President Trump’s executive orders to be enacted in the future, such as his order to end birthright citizenship for children born to undocumented immigrants.