Some restrictions are strict liability, whereas others require some element of intent to use the weapon for an illegal purpose.
Some laws allow the accused a defense to the charge that the item in question was going to be used for a specific set of lawful purposes, such as one's occupation (examples are sets of knives carried by a line cook en route to his job, or tools carried by a construction worker or craftsman).
In this case, the burden of proof is often placed on the accused, requiring them to prove their lawful intent in court.
Other laws require proof of specific intent to commit a criminal act by the accused, thereby placing the burden on the state to produce evidence that the weapon was possessed with some unlawful purpose (such as an attempted homicide, robbery, or assault).
[3] For civilians, permits can sometimes be obtained to possess or carry certain weapons if that person meets certain qualifications that show they can be trusted (such as safety training and lack of prior criminal behavior) and/or have a specific need for the weapon, for example if the nature of their job places them at high risk for assault or robbery.