The article mentions that most of the knives would have been law-abiding when sold, but due to wear, the blade hinge loosens enough that an officer can flick it open.
So it's a compliance issue. Then the law is fine. A person should be responsible for keeping their property legally compliant, be it automobile, knife or propane tank.
Keeping an automobile or propane tank in poor maintenance is likely going to end in an innocent third party being harmed. Not keeping your knifes sharp and properly "detented" is only going to wind up hurting the person who owns that knife.
