In a landmark enforcement of Nassau County’s new face mask ban, police in the suburbs of New York City have made their first arrest under the local law, officials announced this week.

On Sunday night, Nassau County Police responded to reports of a suspicious individual near the Levittown and Hicksville town line, on Long Island about 30 miles east of Manhattan.

Upon arrival, officers encountered Wesslin Omar Ramirez Castillo, who was dressed in black clothing and wearing a black ski mask that covered his face except for his eyes.

The department reported that the 18-year-old exhibited other suspicious behavior, including attempting to conceal a large bulge in his waistband and failing to comply with officers’ commands.

Upon inspection, the bulge was revealed to be a 14-inch knife. Mr. Ramirez Castillo was promptly arrested without further incident.

He was arraigned on Monday in Nassau County District Court at Hempstead on misdemeanor charges of criminal possession of a weapon and obstructing governmental administration, as confirmed by the office of the Nassau County district attorney, Anne Donnelly.

Additionally, a spokesman for the police department, Lieutenant Scott Skrynecki, said that Mr. Ramirez Castillo would also face a misdemeanor violation of the face mask law in the coming days.

The Nassau county executive, Bruce Blakeman, who signed the mask ban into law earlier this month, praised the arrest as evidence of the law’s effectiveness.

“Our police officers were able to use the mask ban legislation as well as other factors to stop and interrogate an individual who was carrying a weapon with the intent to engage in a robbery,” Mr. Blakeman said in a statement. “Passing this law gave police another tool to stop this dangerous criminal.”

The attorney-in-chief at the Legal Aid Society of Nassau County, Scott Banks, who is representing Ramirez Castillo, disputes this justification.

“There is no basis to believe that wearing a face mask was intended to conceal identity or criminal behavior, and if that was the basis of the stop I believe there is a basis to conclude the stop was unlawful,” Mr. Banks wrote in an email to the AP.

The Mask Transparency Act, passed by Nassau County’s Republican-controlled legislature, was introduced in response to a rise in antisemitic incidents reportedly perpetrated by individuals wearing masks since the October 7 start of the Israel-Hamas war.

The law classifies it as a misdemeanor, punishable by up to a year in jail and a $1,000 fine, for anyone in Nassau County to wear a face covering to hide their identity in public.

Exceptions are made for masks worn for health, safety, religious, cultural reasons, or during peaceful celebrations where masks are customarily worn.