NFL Teams Can No Longer Block Assistants From Coordinator Interviews, via Sports IllustratedAll can be blocked from being hired if their teams don't want them to leave.
https://www.si.com/nfl/chargers/news/nfl-teams-block-assistants-coordinator-interviews-changes#:~:text=News-,NFL Teams Can No Longer Block Assistants from Coordinator Interviews,coordinator positions with other clubs.