New York Jets defensive lineman Quinnen Williams was arrested at LaGuardia on Thursday ... cops tell TMZ Sports the former 1st-round pick brought a gun to the airport.
Law enforcement sources tell us Williams was going through a security checkpoint at around 9:15 PM ET when TSA agents scanned his luggage and found a Glock 19.
The way it was put to us ... Quinnen told officials he believed he could carry the gun into New York legally ... since the 22-year-old does have an Alabama permit for the firearm.
But, after authorities explained to the 6'3", 303 pound NFL player he had to have an NY permit to carry there .