You're right. Stewart is a no rifle zone. Bring a rifle, and receive a ticket.
You are allowed shotguns, muzzle loaders, bows, and air guns. During the non-deer season, you are not allowed access to interior roads and must park outside. During deer season, you are allowed access to interior roads and parking spots.
There are a lot of rules to Stewart, be sure to know them all or face fines as it is heavily patrolled by Rangers and DEC.