The power of government to enact laws in the interests of the public health, safety and welfare of the people is called the “police power.” The police power is at the core of local and state authority to regulate firearms and firearms dealers. However, under our federal system, Congress has only those powers delegated to it in the United States Constitution. Except with respect to the District of Columbia and the federal territories, the police power is not one of the powers delegated to Congress. The principal powers available to Congress to regulate firearms are the “commerce power,” arising from the Commerce Clause, and the “taxing power,” arising from the Taxing and Spending Clause.
A regulation based on the exercise of the taxing power must be consistent with that power. The first federal regulation of firearms, the National Firearms Act (“NFA”), was enacted as part of the Internal Revenue Code in 1934. The NFA levied taxes on the manufacture, sale and transfer of certain classes of firearms and enacted regulatory provisions related to the collection of those taxes. Similarly, a federal regulation based on the exercise of the commerce power must be consistent with the limits on that power. In general, Congress may exercise its commerce power to regulate channels of interstate commerce (i.e., commerce across state lines), the objects moving in interstate commerce and activities which have a substantial relation to interstate commerce. Many of the more recent federal firearms regulations have been enacted through the commerce power.
While congressional authority to regulate firearms is constrained by the nature of the powers delegated to it, the police power of state governments is broad and flexible. As a general rule, once a state legislature identifies a public health or safety problem and enacts a law to address that problem, the courts will presume that law to be valid, and will overturn it only if it is unreasonable, clearly arbitrary, or has no foundation in the police power. Under most state constitutions, local governments are also vested with police power. Thus, in most states the police power of local government will be as broad as that of the state in which it is located, unless the state legislature has enacted a law taking away (“preempting”) the power of local governments to regulate a given subject. (To learn more about preemption and the distribution of power in a specific state, find the state you are interested in on the home page map, click on the state, and go to "state preemption.")
In some circumstances a state or local government’s power to regulate a given subject may be taken away (“preempted”) by the federal government. The concept of “federal preemption” derives from the U.S. Constitution’s Supremacy Clause. However, the general rule is that a state law is not preempted by federal law on the same subject unless Congress has manifested a clear, unambiguous intent to deprive the state and local governments of their power to regulate that subject.