This is going into feasability and away from morality, but ok.

The law is the “mutually agreed contract”, and the usage created the dept. You can be expected to know that the design of a bridge might be copyrighted, you can’t be expected to know that a bridge is private property and crossing it requires a fee. Ergo it’s on you to contact the owner of the design, and it’s on you to collect a fee from people using your bridge if that is what you want to do.