Creating the data for that transaction is protected as a right but using it as money doesn't mean that it is immune from other laws.
What does it mean to use it as money? What if instead of using it as money you just say it, post it to a website, email it, or broadcast it to a peer? Are any of those things protected speech?
Those all likely would be forms of protected speech, and there is nothing I know of saying there is any legal issue with you doing so. However, if that protected speech was for the purpose of transacting bitcoins on my behalf that action might make it so that you would be required to register as a money service business and file reports with the government, for instance.