SEATTLE, WA – Washington Attorney General Nick Brown on Wednesday said he expects the 9th Circuit Court of Appeals and the U.S. Supreme Court to rule in the state’s favor in a lawsuit challenging President Donald Trump’s executive order ending birthright citizenship.

Brown’s office filed the lawsuit in the U.S. District Court of Western Washington on Jan. 21. The lawsuit claims Trump’s order would affect thousands of children born in the U.S. to parents living in the country illegally. Those children are currently granted automatic citizenship under the 14th Amendment. Oregon, Arizona, and Illinois joined Washington’s complaint.

The 14th Amendment – ratified in 1868 – states that “all persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.

During Wednesday’s 9th Circuit Court of Appeals hearing – the first time the merits of Trump’s executive order have come before a federal appeals court – Eric McArthur, deputy assistant attorney general for the Appellate Staff of the Civil Division, argued on behalf of the Trump administration that illegal aliens did not exist when the U.S. ratified the 14th Amendment. Trump’s executive order argues that the 14th Amendment’s protections for citizens apply to those “subject to the jurisdiction thereof.”

“Domicile” was mentioned multiple times during the hearing. Domicile refers to a person’s permanent legal residence and is a legal concept used to determine jurisdiction for taxes and voting. McArthur argued that domicile is required for full and complete jurisdiction.

Brown remains steadfast in his belief that the executive order is illegal and the president does not have authority to decide who is granted citizenship.

“What they have been arguing today – is to overturn over a century of law and precedent in Supreme Court holdings in the United States,” Brown said outside of the courthouse after Wednesday’s hearing. “We’re talking about overturning the fundamental understanding of what it means to be an American in this country.”

He went on to say, “I’m really confident moving forward that this court and ultimately the Supreme Court will rule in the state’s favor.”

There have been multiple nationwide injunctions issued against the executive order Trump signed seeking to end birthright citizenship. These injunctions were issued by federal judges in Maryland, Massachusetts and Washington.

Last month, the U.S. Supreme Court heard a case related to Trump’s executive order ending birthright citizenship. The high court’s future ruling in that case could not only impact birthright citizenship, but also answer once and for all whether lower courts have the power to block Trump’s orders nationwide.

The three-judge panel in the 9th U.S. Circuit Court of Appeals is expected to issue a written ruling in the coming weeks or months. The appeals court may wait until the Supreme Court rules on the question of nationwide injunctions.