Usually the embarrassing information is published before the embarrassed party is aware that their dirty laundry is about to go public. Once the information is out there, a copyright infringement suit is usually an irrelevant or losing move for managing the politician's image. I would rate this story worse for Biden if he filed a copyright infringement suit against the computer repair guy or the Post, for example. Using copyright could prevail legally yet lose in the more politically important court of public opinion.