Nassau County’s ban on transgender athletes from competing on women’s sports teams in county-owned facilities was upheld Monday by a state Supreme Court judge.

Justice Bruce Cozzens ruled that Nassau’s law is legal and does not exclude transgender athletes from competing on county property and using the restrooms “in accordance with one’s biological sex.”

Cozzens, in his decision, wrote the county’s law is meant to “protect women and girls in sports.”

The justice cited a Tennessee court ruling from last year that allowed schools to separate facilities based on biological sex “without accommodating gender identity.”

“We are grateful that the court found our legislation to be valid and legal,” Nassau County Executive Bruce Blakeman, who signed the bill into law in 2024, said in a statement.

“We will continue to protect girls and women from unsafe and unfair competition,” said Blakeman.

Seth Koslow, a Democrat running against Blakeman who voted against the bill when the GOP-majority legislature passed it last June, declined to comment.

Shortly after the ban became law, the Long Island Roller Rebels — an adult recreational women’s roller derby league based in Nassau over the last two decades — sued the county and was represented by the New York Civil Liberties Union.

Gabriella Larios, the NYCLU attorney representing the league, argued the law is discriminatory and violates human and civil rights laws by forcing transgender athletes to use private facilities.

Monday’s ruling  effectively etched the ban in stone, and ended the lawsuit altogether, with the judge granting the county’s motion to end the case and throw out the suit.

The edict affects more than 100 public facilities in the county of nearly 1.4 million residents just east of Queens.

“Today’s decision sends a chilling message that trans people don’t belong in Nassau County, but the fight doesn’t end here,” said Larios, who claimed the ruling “flies in the face of longstanding state law.

“Despite this setback, we will challenge this decision to ensure trans girls and women can play sports freely, just like everyone else — we are confident that New York courts will ultimately see the ban for what it is –– unlawful and discriminatory,” Larios added.

A separate lawsuit filed by New York Attorney General Letitia James last year against Nassau County over the same law is still active.

In her suit, James also argued the law violates state human and civil rights laws.

“Here in New York, every person has the right to be exactly who they are free from discrimination, and my office will always protect that right,” James said in a statement accompanying the lawsuit.