Not sure if anyone of you have been in a similar situation but when I was the acting president for a student association, one of the executives did several tasks without my consent which is obviously wrong! Approval needs to be made by the president.
If people are not going to treat you like a leader or even obey you, that’s a problem. Normally there’s a gap between the leader and the executives below them. Maintain that gap because when there is a gap, there is respect. When the gap shortens, respect will decrease. Leaders needs to maintain respect and give no coworker a reason to disobey them and take advantage of them.