From usconcealedcarry.com:
Maine is a
shall-issue,
permitless carry state with concealed weapons permits issued at the state level by the Department of Public Safety through the Maine State Police.
There is no permit, background check or firearms registration required to buy a handgun from a private individual.
Open and
concealed carry are legal in Maine without a permit. Any person 21 or older, or at least 18 and active duty or honorably discharged military, who can legally possess a firearm, is allowed to carry openly or concealed. In addition, Maine issues permits for reciprocity purposes.
Maine Permits to Carry Concealed Handguns (CCHs) require a firearms training course that has been approved by the state. Maine CCHs are issued to residents and non-residents that are at least 18 years old. Some areas are off-limits, including schools and courthouses. In terms of
reciprocity, since Maine has permitless carry, any person at least 21 years old who can legally possess a firearm may carry a concealed firearm on his or her person without a license or permit. In addition, Maine also recognizes resident concealed handgun permits issued by another state if that state recognizes Maine’s resident CCHs. Permit holders from these states are allowed to carry in a few areas that individuals who carry under the permitless carry law cannot, including Acadia National Park.