AITA for not letting my boyfriend go on a trip with his ex?

I have been dating my boyfriend for 3 years now and we have been living together for 1 year. <br><br>He’s great, and I do love him but I just don’t want to break up. <br><br>I have a little concern though. His friend group is made up of his best friends from high school and college. They have a group chat and normally he’s in it. I don’t mind. <br><br>His ex from high school “Joan” is in the group chat and is friends with him. Again, I’m ok with it. <br><br>They were texting each other yesterday and I don’t mind. <br><br>However, Joan asked him to go on a trip and he said yes. It was a trip to a beach on the gulf coast. I don’t like it.<br><br>He got upset and got upset when I asked him to stay home and not go. He got upset and said he could go but I could not say no. He said he was going to go anyway and that I have no right to tell him no.<br><br>I said to him that I have a right to say no because I am his girlfriend. He just got upset again.<br><br>AITA?