In theory, but in practice getting a patent invalided is a fraught and unreliable process. The courts have been generally deferential to the the USPTO decision

In theory, but in practice getting a patent invalided is a fraught and unreliable process. The courts have been generally deferential to the the USPTO decision, which may be a problem if some examiners have allowed patents to go through on the assumption that the courts can fix it later if they get it wrong.