JACOB SULLUM: Gravity Knives, Bump Stocks, and Lawless Law Enforcement. “New York cops and the president arbitrarily turn legal products into contraband.”

Last week Cracco, a Manhattan sous chef, won a federal lawsuit he filed after he was arrested for violating New York’s 1958 ban on “gravity knives.” That law makes it a misdemeanor to possess “any knife which has a blade which is released from the handle or sheath thereof by the force of gravity or the application of centrifugal force which, when released, is locked in place by means of a button, spring, lever or other device.”

For years Cracco had been using his Spyderco Endura 4 folding knife, the sort of tool that is sold openly by retailers in New York City and throughout the state, for mundane tasks like opening boxes and bottles. On a Friday afternoon in October 2013, Cracco was standing on a subway platform, heading home to Connecticut, when a police officer spotted the knife clipped to his pants pocket and subjected it to the NYPD’s notorious “wrist flick test.”

According to Cracco and a co-worker who was with him, it took the cop four or five tries before he managed to swing the blade fully open with one hand—a feat that Cracco himself had never attempted. Cracco thus joined the thousands of New Yorkers who are arrested each year for carrying the tools of their trades or hobbies.

“Because the wrist flick test is a functional one, it is difficult if not impossible for a person who wishes to possess a folding knife to determine whether or not the knife is illegal,” U.S. District Judge Paul Crotty noted in a March 27 decision declaring the gravity knife ban “unconstitutionally vague” as applied to Cracco. “People should be able to tell whether their conduct is lawful or unlawful.”

Where’s the fun for lawmakers or police in that?