That is not true. If it's pre 1898 it's antique, beyond that it is classified as a destructive device and has a whole bunch of red tape. Anytime you see words $200 tax stamp it isn't easy to get.
And even a pre 1898 cannon is going to cost you $8k+ for a rusted out POS that will explode if you try to actually fire it.
Social with the joke being Chinese people can't pronounce L and R properly and swap them.