Are butterfly knives illegal in new york state?

no they're not

They Are ILLEGAL in New York State. They are classified as a gravity knife which includes centrifugal force to open it. nys penal law 265.00 sub 5.

Correction:

Several court cases have ruled that a buttefly knife does not match the legal definition of a gravity knife, therefore they are legal:

In People v Zuniga, 303 AD2d 773, 759 NYS2d 86 (2d Dept 2003), the Appellate Division held that possessing a "butterfly knife" did not constitute a "gravity knife." The butterfly knife requires manual locking and thus does not come within the definition of "gravity knife."

Similarly, in People v Mott, 137 Misc2d 757, 522 NYS2d 429 (County Ct 1987), the judge inspected the knife and recorded his observations: "Such a knife is a folding knife with a split handle. In the closed position, the knife is covered on each side and at the point by two metal guards attached to the blade's base. To open the knife, the metal guards are folded back until they meet and are clasped and thereby form a handle for the blade." Again, the court held that the butterfly knife did not constitute a "gravity knife."

In People v Dolson, 142 Misc2d 779, 538 NYS2d 393 (County Court 1989), the judge stated: "While this appears to meet the first part of the statutory definition of a gravity knife, an important difference exists here. The blade of the knife recovered from Appellant does not lock into place 'when released' from its cover."