It is not accurate to say that samurai swords, specifically known as katana, are illegal in general. The legality of owning a katana or any bladed weapon depends on the specific laws and regulations of the country or jurisdiction in question.

Different countries have varying laws regarding the possession, sale, and use of bladed weapons, including swords. In some places, there may be restrictions on owning certain types of swords or regulations regarding their length, blade material, or sharpness. These laws are generally in place to ensure public safety, prevent misuse, and regulate the possession of potentially dangerous weapons.

Regarding Japan specifically, as mentioned earlier, there are regulations governing the possession and trade of traditional Japanese swords, including katana. The Japanese Sword and Firearms Control Law (Sword Law) is in place to control the circulation and protect the integrity of Nihonto, which includes katana. However, it is worth noting that individuals in Japan can obtain a license to legally possess and trade Nihonto, including katana.

In other countries, such as the United States, owning a katana or any bladed weapon is generally legal, but there may be restrictions on carrying them in public or using them for criminal purposes. However, laws can vary at the state or local level, so it's important to familiarize oneself with the specific regulations in a given jurisdiction.

It is crucial to understand and comply with the laws and regulations regarding bladed weapons in your specific location to ensure that you are in legal possession of any sword, including samurai swords or katana.