Possession of Unregistered Firearm Possession on Vessel by United States Citizen or Resident Alien is a federal offense in the United States. It is illegal for a U.S. citizen or resident alien to possess an unregistered firearm on any vessel, including a boat, ship, or aircraft, without a valid federal firearms license. There are two types of Possession of Unregistered Firearm Possession on Vessel by United States Citizen or Resident Alien: 1. Unlawful Possession: This is the possession of an unregistered firearm on a vessel without a valid federal firearms license. This offense can result in a fine of up to $250,000 and/or imprisonment of up to 10 years. 2. Knowingly Possessing an Unregistered Firearm: This is the possession of an unregistered firearm on a vessel with knowledge that the firearm is unregistered. This offense carries a maximum penalty of $500,000 and/or imprisonment of up to 20 years.