In the United States, the legality of owning and possessing katanas, or any other type of sword, can vary depending on state and local laws. Sword regulations are generally determined at the state level, so it's important to understand the specific laws in the state where you reside or plan to possess a katana.

While I can't provide a comprehensive list of laws for every state in the US, I can provide some general information:

1. Legality: In most states, it is legal to own a katana or other types of swords as long as they are used for decorative purposes or as part of a collection. However, some states have restrictions on blade length, types of swords, or the intent of use. There are states where certain types of swords, such as double-edged blades, may be prohibited or require a permit to possess.
2. Carrying and Concealment: Even in states where sword possession is generally legal, carrying a sword in public or concealing it may be subject to specific regulations. It is important to check local laws and understand whether there are restrictions on carrying a sword outside of your private property.
3. Federal Regulations: At the federal level, there are no specific regulations that prohibit the ownership of swords, including katanas. However, if a sword is classified as an antique or falls under specific categories, such as those regulated by the National Firearms Act (NFA), additional restrictions and regulations may apply.

To ensure accurate and up-to-date information regarding the legality of owning katanas in your specific state, it is crucial to consult the relevant state laws, local ordinances, or contact local law enforcement agencies. They will be able to provide you with the most accurate and detailed information based on your location.