Criminal possession of a weapon
Criminal possession of a weapon is the unlawful possession of a weapon by an individual. Many societies both past and present have placed restrictions on what forms of weaponry private citizens (and to a lesser extent police) are allowed to purchase, own, and carry in public. Such crimes are public order crimes and are considered "mala prohibita", in that the possession of a weapon in and of itself is not evil. Rather, the "potential" for use in acts of unlawful violence creates a perceived need to control them. Some restrictions are strict liability, whereas others  require some element of intent to use the weapon for an illegal purpose. Some regulations allow a citizen to obtain a permit or other authorization to possess the weapon under certain circumstances. Lawful uses of weapons by civilians commonly include hunting, sport, collection and self-preservation. Types. Criminal possession of a weapon generally falls into one of several categories: Strict liability vs. specific intent. All weapon possession crimes follow some standard of intent (mens rea), though this standard varies. The most common is "strict liability," meaning that there is no requirement of intent whatsoever: Merely being caught by law enforcement  with the weapon in question under the circumstances described in the law (possession, concealed, or open) is a crime in and of itself, with almost no possible defense other than proving the item is not an illegal weapon within the law's definition. 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). The circumstances under which law enforcement discover the weapon often play a strong role in this. Exceptions. Many laws about weapon possession contain exemptions for persons of specific occupations, or allow for permission to be obtained from  the government to lawfully possess the weapon. Generally, military personnel actively carrying out their duties are exempt from nearly any restriction other than internal policy and international treaties. However, they are often restricted from possessing their issued weapons when they are not on duty. Police often are allowed to lawfully possess certain weaponry above what the populace is allowed to possess, though this varies by nation and jurisdiction. In some nations police may take their armaments home when off duty, while in others they are required to leave all (or some) of them in storage at their station. Some jurisdictions  have special paramilitary units (such as SWAT or AFO) that carry machine guns, explosives or other military weapons, though the majority of the time these must be stored at the unit's headquarters. 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. The most common in the United States  is a permit to carry a concealed handgun for purposes of self-defense. This permit often applies to both firearms and other self-defense implements. In many states, no permit at all is needed to carry a non-concealed firearm or other weapon. Other types of license can be obtained for collection and exhibition purposes, such as under the National Firearms Act. In the UK, a citizen can obtain a firearms or shotgun certificate in order to legally purchase and own rifles or shotguns for the purposes of sport and hunting.