What's with coach interview "permission"?

No, it's not. Teams regularly deny permission because they simply want to hold onto the assistant. Dallas prevented Sparano from leaving for New Orleans with Sean Payton, Tampa kept Rod Marinelli as a virtual prisoner for the longest, etc.

You allow an assistant to interview because
1) It allows you to attract better assistants. If you regularly stand in their way, the best ones will shy away from you (unless your name is Bill Parcells in which case you can get away with it)

2) An unhappy assistant may potentially be an ineffective assistant


I think the poster is talking about coaches interviewing for head coaching vacancies.