how to get off a mailing list?

Does anyone know where I can find the actual scoop on the laws about businesses sending unsolicted (paper) mail? I bought something once from a company years ago (like... 1997? before 2000 at least) and I have been receiving fairly frequent catalogs from them ever since. I realize that for the first year or something they are allowed to do that based on our "established business relationship", but we're way outside that limit. I want to be off their mailing list and I have notified them in writing at least once. That is, I have sent back my name and address from the catalog in their order envelope - this may not comply with the standards of the law in this matter, so I want to know exactly what it is I am supposed to have to do to count as notifying them that I wish to be removed from their mailing list, and how to make the formal complaint to get them to stop / collect a fine from them if they still don't stop.

how to get off a mailing list?

Does anyone know where I can find the actual scoop on the laws about businesses sending unsolicted (paper) mail? I bought something once from a company years ago (like... 1997? before 2000 at least) and I have been receiving fairly frequent catalogs from them ever since. I realize that for the first year or something they are allowed to do that based on our "established business relationship", but we're way outside that limit. I want to be off their mailing list and I have notified them in writing at least once. That is, I have sent back my name and address from the catalog in their order envelope - this may not comply with the standards of the law in this matter, so I want to know exactly what it is I am supposed to have to do to count as notifying them that I wish to be removed from their mailing list, and how to make the formal complaint to get them to stop / collect a fine from them if they still don't stop.