What Happens If You Are In A Group Chat With Someone You Blocked Snapchat?

The group conversation continues as before with no changes. You will still be able to communicate with them while using it. It is probable that their name will be changed to reflect their real user name. When they join the group chat for the first time after blocking you, they will get a notification that alerts them to the fact that they are entering a conversation with someone who they have previously blocked.