(ABC 6 News) — A monumental case went before the Supreme Court on Thursday involving President Donald Trump’s executive order ending birthright citizenship.

It is part of the president’s efforts to curb illegal immigration, but birthright citizenship is enshrined in the Constitution.

Some of the justices appeared skeptical, but Justice Clarance Thomas leaned the other way, suggesting that limiting the power of local judges may be on the table.

The high court could issue a ruling as soon as next month.