The gravity flip test is one that some authorities in various jurisdictions like to apply to any folding knife in the possession of somebody whose day they want to ruin, for good reason or some other kind of reason.
A year or so ago, I spent a couple of days down at the Los Angeles County Criminal Court as an "expert witness" hired by the public defender, to show the jury why the "flipping it open with ten tries" test was an abusive construction of the statute. The dope-dealing bum who owned the cheap POS knife was acquitted on the knife charge, and the county never did pay my bill.
The language in Section 653K of the California penal code regarding thumb-operated one-handers would appear to legalize any knife with a thumb stud or blade hole, even though there is another way to open it, i.e. flipping or maybe even the push button of a DA auto. CAUTION - That theory has not been tested in court!
I can't speak for other states.
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- JKM
www.chaicutlery.com