I do not believe there is such a thing as an API for copyright assignment. You probably require real life paperwork in the form of a contract. That or you can w

I do not believe there is such a thing as an API for copyright assignment. You probably require real life paperwork in the form of a contract. That or you can wait until you get the opportunity to test out your smart contract to see if it survives a court challenge. I wouldn't be able to predict the results of such a test. As always on these types of questions. I am not a lawyer this is not legal advice.