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.

Federal courts have so far uniformly blocked President Donald Trump’s order seeking to end birthright citizenship for children born in the United States to someone in the country illegally.

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.