If you chose to manually assign reviewers from the PC console, that means that assignments are based solely on group membership. For example, anyone in the Paper1/Reviewers group will have reviewer permissions for Paper 1. If you removed them from that group, they would be effectively unassigned from Paper 1 and would lose access to those permissions. Note that the following steps should only be used for venues that used manual assignment through the PC console. Do not do this if you used the edge browser.