KnifeUp provides free knife law guides for all 50 states. Click on the state you are interested in to read about its knife laws. I try to keep these guides as up-to-date and accurate as possible but laws do change so please leave a comment if you see something wrong.
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How the US Justice System Works
The United States was founded under the principle of federalism. Under federalism, governing powers are divided between the federal and state governments. For states that existed before the founding of the US, the writers of the Constitution respected the states’ authority by limiting federal powers to only those expressly stated within the Constitution. All other governing powers are, theoretically, state powers.
For knife laws, the only federal law is the Switchblade Knife Act of 1958 as well as the 2009 amendment to the act (see 15 U.S.C. 1244). The federal knife law primarily applies to individuals who are traveling between states or internationally. However, if you reside in a federal district (see Washington D.C. knife laws), the federal law does govern knives for you. If you live in one of the 50 states, the federal law would only apply to you if you are traveling from one state to another or if you are entering federal property, such as a military base.
All states have knife laws but some knife laws by state are more up-to-date than others and local municipalities often pass their own knife laws as well. For example, if you live in Denver, Colorado, you must abide by the knife laws of Colorado as well as the knife laws of Denver. However, if you travel to Boulder, Colorado (30 minutes away) you must conform to the knife laws of Boulder, instead of Denver, in addition to Colorado’s. And, during your journey, you must conform to the knife laws of all the municipals in between Boulder and Denver.
This makes knife laws by state a tricky subject unless your state has a preemption clause. Preemption means that the state government nullifies all knife laws made by cities and counties. Therefore, when you travel from town to town, you would not have to worry about municipal knife laws.
General Guide to Knife Laws
Knife laws can be divided into these two categories: ownership laws and carry laws.
Ownership laws forbid individuals from owning certain types of knives that society has deemed “deadly weapons” or “dangerous.” Most of the time, these knives were once associated with unlawful people such as gangs, the mob, and outlaws. It is for this reason that the Bowie knife has been outlawed in so many states.
Carry laws forbid an individual from carrying, concealed or open, certain knives. For example, some states forbid an individual from conceal carry of knives over a certain length but open carry of that same knife is legal. Other states forbid the carry, concealed and open, of certain knives. Most knives that are barred from carry are ones deemed by society to have no utility uses and, therefore, their only use is as weapons.
Some states have laws that forbid one from aggravated display of a knife as well as committing a crime with a knife. These laws are usually only enforceable after the fact and, for that reason, allow the state to increase the penalty of a crime. For example, robbery with a knife is considered a more serious crime than simple robbery.
What is Generally Allowed
If you want to carry a knife that is usually legal everywhere, I highly recommend you buy a knife that is clearly intended for utility use. For example, most pocket knives and almost all leathermans and multi-tools fit this description. As long as the blade is less than 2.5 to 3 inches, you should be fine. Locations that may be exceptions to this general rule are courts, planes, schools, and special buildings that forbid the carrying of knives.