Backers of the measure say legalizing switchblades would eliminate a need for one-armed people to be forced to open folding knives with their teeth in emergencies.
The bill to allow amputees and other one-armed people to carry the quick-opening knives cleared Maine's Senate on Wednesday after passing the House on Tuesday, Senate officials said.
Until now, Maine banned the use of switchblades by anyone.
In most states, carrying switchblades is illegal in most circumstances, though owning the knives may be allowed in some states.
Federal law allows their use by a person with one arm only on federal property if the blade is shorter than three inches.
The Maine bill requires that the knives have a blade that is three inches or shorter.