No they didn't work. The law stopped that purchase the perp still found a way. Someone hell bent to commit a crime WILL find a way. Yesterday in China, 20 schools kids were killed with a knife.
Please keep the facts straight. While I agree with your primary contention that people out for retribution will find a way to arm themselves with as lethal a weapon as possible, misstating the facts doesn't help make your point.
“Yesterday in China, 20 schools kids were killed with a knife.”
There were no deaths; 22 students were injured.