Oh okay then let's just give them an infinite gun and ammo cheat as well. Because why the fuck not.https://en.wikipedia.org/wiki/2014_Kunming_attack - 10 people with knives kill 33.
https://en.wikipedia.org/wiki/School_attacks_in_China_(2010–12) - One guy kills 8 kids.
http://www.bbc.com/news/world-europe-33847070 - Man with knife kills 2 and injures 1
If someone wants to kill, they'll find a way.
This "we don't need laws/regulations, where's a will there's a way" is grade school level reasoning.