In this case, couldn't it be argued that as an import US Customs allowed it into the country and because US Customs wouldn't allow a "gravity" knife into this country that ergo said knife is not a "gravity" knife. Bolster this with the fact that it's not designed as a gravity knife and you have the start of your arguement.
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~ JerryO ~
Cogito Cogito Ergo Cogito Sum
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~ JerryO ~
Cogito Cogito Ergo Cogito Sum