How Do You Know If Your Knife Is Legal?

From Copeland v. Vance, 230 F. Supp. 3d 232(SDN.Y. 2017:

To meet the first statutory requirement of the Gravity Knife Law, it is clear that a knife need not open by both gravity and the application of centrifugal force; if a knife opens by centrifugal force alone and the blade locks in place once released, the knife is an illegal gravity knife. ...

For instance, during questioning regarding Native Leather his deposition, plaintiffs asked D.A. Rather: "And did you ever have the circumstance arise where a knife passed the functional test with one person, but failed it with another?" (Rather Dep. 43:15-17.) D.A. Rather responded: "In a fashion. Gravity knives by law don't have to open each and every time. . . ."