I'm not up to date on Maine Knife Laws myself, but I can point out one valid loop hole for you.
Maine - Chapter. 25 252. Section 2001A. Threatening display of or carrying concealed weapon:
1. Display or carrying prohibited. A person may not, unless excepted by a provision of law:
A. Display in a threatening manner a firearm, slungshot, knuckles, bowie knife, dirk, stiletto or other dangerous or deadly weapon usually employed in the attack on or defense of a person; or
B. Wear under the person's clothes or conceal about the person's person a firearm, slungshot, knuckles, bowie knife, dirk, stiletto or other dangerous or deadly weapon usually employed in the attack on or defense of a person.
2. Exceptions. The provisions of this section concerning the carrying of concealed weapons do not apply to...
C. Knives used to hunt, fish or trap as defined in Title 12, section 10001;
Maine - Chapter. 12 Section 10001. Definitions.
23. Fish, the verb. To "fish" means to take, catch, kill, molest or destroy fish or to attempt to take, catch, kill, molest or destroy fish.
31. Hunt. To "hunt" means to pursue, catch, take, kill or harvest wild animals or wild birds or to attempt to catch, take, kill or harvest wild animals or wild birds.
64. Trap, the verb. To "trap" means to set, place or tend a trap within the fields, forests or waters of the State, to kill an animal that is caught in a trap or to aid or assist another person in setting or placing a trap, tending a trap or killing an animal that is caught in a trap.