Not sure about the US, but in europe they want you to wear you pack in front of you. A bit of a pain the back side, especially with the airbag packs (needs more buckes to be closed and there is a strap does goes from under your crotch.). But quess that would prevent some of these issues.
I have always skied with a knife, but it's a opinel and i carry it because i'm to cheap to buy lunch and need something to cut my baquette...
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