Are you allowed to buy a katana?

I'm curious, are there any restrictions or regulations surrounding the purchase of a katana? I understand that swords can be dangerous if not handled properly, so I'm wondering if there are any legal considerations or limitations I should be aware of before making such a purchase. Additionally, I'm interested in knowing if there are any specific rules or regulations that vary depending on the location where I plan to purchase and use the katana. Can you provide some clarity on this matter?