Knife legislation is defined as the body of statutory law or case law promulgated or enacted by a government or other governing jurisdiction that prohibits, criminalizes, or restricts the otherwise legal manufacture, importation, sale, transfer, possession, transport, or use of knives.

A gravity knife is a knife with a blade contained in its handle, and that opens its blade through the force of gravity. This mechanism of opening is fundamentally different from the switchblade, which extends its spring-propelled blade automatically upon the push of a button, switch, or fulcrum lever. The main purpose of gravity opening is that it allows opening and closing to be done one handed, in situations where the other hand is occupied. Hence, historically they have been issued to parachutists to cut off caught lines, such as lines tangled in trees, a major potential use of the gravity knife.