Unfortunately for you j', you ran into a LEO who can't distinguish between the letter of the law and discretion. Out of the over 600,000 LEO's across the country, there are bound to be a few of them. We are not all like that, thank God!
As for RH's comment "Too late now, but I don't believe confiscation without a charge or arrest is legal. It's known as "theft".",
I have to disagree.
I have confiscated several illegal knives w/o arrest. The real term is "Officer Discretion", and you do not have to arrest to confiscate an illegal item. Under Penal Law Section 265, in New York State, it is illegal to merely possess a "gravity knife". No intent to use it illegally is required.
Perhaps you don't want to stir the s*** and make it stink, but if you do not feel you possessed a gravity, contact the Sheriff (not the deputy who took it) and see where it goes. But remember this - if it is deemed you did possess a true "gravity knife", you could still be arrested. You may be talking to a Sheriff who also follows the letter of the law, and wishes an arrest to be made!! If the knife was truly confiscated, it should have been logged as evidence and secured.
Sounds like you've been inconvenienced enough already.
No easy answers for you on this one.
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Chris Hatin
http://www.hatintec.com
"Are you ready for the defendant, Judge?"
"Yup. Bring the guilty bastard in."