Quinnen Williams, a defensive lineman for the Jets who was the third player chosen in last year’s N.F.L. draft, was arrested on a weapons possession charge on Thursday night while trying to board a flight at La Guardia Airport, the authorities said.

He was taken into custody around 9:15 p.m. at the Delta Air Lines check-in counter after he was found to have a Glock 19 pistol, according to the Port Authority police. The gun was discovered in Williams’s checked baggage, the authorities said, and it was unloaded.

The authorities said that Williams, 22, had a permit for the weapon in Alabama, where he was a standout player for the University of Alabama, but he did not have one for New York. The matter has been referred to the Queens district attorney’s office.

Williams’s destination from LaGuardia was not immediately clear. Alex Spiro, a lawyer for Williams, said his client “respects and follows the law.”

“There was allegedly a technical issue with the manner in which the lawfully owned firearm was stored — and we expect the matter to be resolved shortly,” Spiro said on Friday.

The Jets said in a statement: “We have been in contact with Quinnen Williams and are fully aware of the situation. We will have no additional comment as this is a pending legal matter.”

Williams recorded 15 tackles and two and a half sacks in his rookie season. He signed a four-year, $32.5 million contract with the Jets, according to the salary tracking website Spotrac.

Williams has an older brother, Quincy Williams, who plays for the Jacksonville Jaguars.