They are legal in some states and illegal in others..
U.S. state laws regarding possession, concealed and non-concealed carry State Possession Carry
Alabama Legal
Alaska Illegal
Arizona Legal
Arkansas Legal
California Legal - Allowed if blade is under 2 inches
Colorado Illegal
Connecticut Legal
Delaware Illegal
Florida Legal - Allowed if not concealed. Concealed carry allowed with permit
Georgia Legal
Hawaii Illegal
Idaho Legal
Illinois Illegal
Indiana Illegal
Iowa Legal
Kansas Illegal -
Kentucky Legal
Louisiana Illegal
Maine Illegal
Maryland Legal
Massachusetts Legal
Michigan Illegal -
Minnesota Illegal - with exceptions made for collectors and/or possession as curios or antiques -
Mississippi Legal -
Missouri Illegal - with exceptions made for collectors and/or possession as curios or antiques
Montana Illegal - with exceptions made for collectors and/or possession as curios or antiques
Nebraska Legal
Nevada Legal - with permit
New Hampshire Legal - Only Possession with intent to sell banned,
New Jersey Illegal
New Mexico Illegal
New York Legal - for the purpose of hunting or fishing if possessed by a person who has a valid hunting or fishing license
North Carolina Legal
North Dakota Legal
Ohio Legal - purchases only allowed through online retailers
Oklahoma Legal
Oregon legal
Pennsylvania Illegal - with exceptions made for collectors and/or possession as curios or antiques
Rhode Island Legal unless blade is a dagger, dirk, or stiletto
South Carolina Legal
South Dakota Illegal
Tennessee Illegal - with exceptions made for collectors and/or possession as curios or antiques
Texas Illegal - with exceptions made for collectors and/or possession as curios or antiques
Utah Legal
Vermont Illegal
Virginia Illegal if for sale, and possession is prima facie evidence of intent to sell. -
Washington Illegal
West Virginia Legal
Wisconsin Illegal
Wyoming Legal