What's the laws on passing a mopedon a solid line?

I was driving earlier today and I was behind a moped which was going about 15 because where I am it's hilly. There was traffic backing up behind me. So I passed them. Am I in the wrong for doing that can I get a ticket? There was no law enforcement around but there was a school bus behind me and other traffic. I didn't know what was the right thing to do. Could I get in trouble for that I see people passing mopeds on solid lines all the time so I have no idea. Just wanted to know how this situation should be handled