At the US Supreme Court Thursday, protesters chanted outside while courtroom sketches captured an unprecedented moment inside, President Donald Trump attending arguments in Trump v. Barbara.

The case centers on whether a president can change who qualifies for citizenship under the 14th amendment.

Trump's executive order seeks to deny citizenship to some children born in the United States based on their parents’ immigration status.

Legal challengers argue that power belongs to the constitution, not the president.

Inside the courtroom, a familiar name from Guam just feet from the President.

“I ended up actually sitting directly in front of President Trump, so I was less than five feet away from him,” said Attorney Neil Weare, Co-Director of Rights to Democracy, an advocacy group for US territories.

He was there representing 21 elected officials and judges from the five territories, who filed a brief urging the court to reject the order.

“It really was an important opportunity to educate the justices that these issues of birthright citizenship is not just about the executive order; There’s also real life issues across the five territories,” said Weare.

The arguments today focused on a key phrase in the constitution, what does “subject to the jurisdiction thereof” actually mean.

For Guam, a different but related question still lingers, what does “in the united states” mean, and whether that fully includes the territories.

“The federal government, congress and the department of justice continue to take the position that if they wanted to, they could deny citizenship to people born in Guam, both moving forward and people who have been citizens their whole life. That’s a very troubling viewpoint and one that’s simply not consistent with the text and history of the Constitution,” said Weare.

Weare says the court did not directly take up that question today, which was expected. Still, there was a significant moment for the territories.

“A strong majority of the court agreed that the citizenship clause was grounded and the historic common law understanding of birthright citizenship, under which birthright citizenship would extend to territories and states alike under that long settled meaning from the founding of the United States, all the way to 1898 when the United States acquired Guam following the Spanish American war,” added Weare.

And despite the President's presence and a conservative majority, justices were skeptical, enough to make the President lash out.

“Because they want to show their independence. Stupid people,” said Trump.

A decision from the Supreme Court is expected in the months ahead.

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What could Trump's birthright citizenship ban mean for Guam?