You're right in thinking law is moral, because morals have a historical character, and a class character, much like laws, and are shaped by the ruling class. However, because you ignore class, you can't properly analyze what "law is moral" means. For example, copyright is moral in capitalism, because it "protects artists' rights" and "copying is stealing" and whatnot. Lobbying is moral, because the entire parliamentary system is set up with the goal of letting the rich "invest" into the political "marketplace of ideas".

However, the fact law is moral under capitalism doesn't mean the law is "eternally" moral. Capitalism is harming humanity, so it must go, alongside its morals. You are right that in the future, copyright won't exist. However, for such a change in the political superstructure, according economical changes are required. Until capitalism is gone, there are no reasons for copyright to magically disappear, and a billion reasons for it to keep existing.