Yes, a felony or breach of the peace committed in your presence. If I smell marijuana on someone, I have probable cause to believe they are committing a felony in my presence. I don’t agree with the law and the feds should repeal it, but it seems like pretty basic textbook stuff to me.
Then you don’t understand the very legal concept of a citizen’s arrest. If someone has probable cause to believe that you have committed a felony or breach of the peace in their presence, then they are performing a very lawful arrest and not an “unprovoked assault.”