Did the Supreme Court extra-legally amend the Constitution?

It is my understanding that the Supreme Court (SC) takes cases primarily (or maybe exclusively?) when there is a question of a particular law being "Constitutional." In many cases they will determine what Congress means by a particular law and based on their understanding of a law determine is it Constitutional. In this immunity case there is nothing in the Constitution about immunity, as far as I can tell this was never discussed, debated or written about in any discussions, letters etc... So what exactly was the SC doing here? It seems to me they did not say any of the laws do not meet constitutional muster. In fact what they have done is either inserted a clause into the constitution and amended it extra-legally. Democrats around the country should realize this and state clearly that the SC does not have a role in amending our Constitution and this ruling, which amounts to an extra-legal amendment does not stand and will not be abided by by any democratic administration.