A multi-tool is legal to carry in most states and countries. Still, it is wise to look through the knife legislation of your place. Some places will only let you carry one for a valid reason. If you'd like to travel with your multi-tool, make sure that it is TSA compliant. Although, we've heard some airplane staff do not let you carry on multi-tools that are even TSA compliant, so to be on the safe side, it's better not to take one with you on a plane.