NEW YORK (AP) — With the flick of a pen, a New York judge ruled Thursday that a sous chef can carry his folding knife because a state law judging gravity knives by a wrist-flick test was too vague.

U.S. District Judge Paul Crotty raised new doubts about the state’s law governing gravity knives with his written decision although the law was recently upheld by the 2nd U.S. Circuit Court of Appeals in Manhattan.

“People should be able to tell whether their conduct is lawful or unlawful,” Crotty wrote.

At stake is a law that Crotty said causes knives to be defined by their function rather than their design. Police officers use a so-called “wrist-flick test” to identify gravity knives. If the blade exits the handle and locks in place automatically with a flick of the wrist, it’s a gravity knife.

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But Crotty said certain folding knives, while not intended to be illegal, can function as gravity knives over time as they wear down or if they are modified. He also said there was no specification of how many times an officer can try to flick a blade out before it gets defined as a gravity knife.

The judge made clear that he was ruling that Joseph Cracco, a Connecticut man, could carry a common folding knife based on his factual circumstances rather than declaring the law unconstitutional. However, Crotty was also critical of the law.

Crotty said the law’s legal history left vague what can be considered a gravity knife. He noted the knives are sold openly in New York stores and the law’s purpose was to ban possession of weapons used in crimes. He said Cracco’s knife is commonly used by cooks, craftsmen and laborers.

Cracco sued New York City and a police officer in 2014 seeking damages for false arrest.

A policeman stopped Cracco in October 2013 when he spotted the blade clipped on Cracco’s pants pocket as he headed home. Cracco used the knife as a sous chef and to open boxes, bottles and when working on cars or motorcycles.

Cracco pleaded guilty to disorderly conduct and paid a fine.

Danny Frost, a spokesman for Manhattan District Attorney Cy Vance Jr., said the office was “reviewing the decision.”