The FAA and a lot of other. Agencies are treading a lot more softly since the recent EPA case caused the future of the Chevron Deference doctrine to be brought into question.

https://www.mcglinchey.com/insights/...vron-doctrine/

and other cases aimed at it are in the queue.

https://www.politico.com/news/2023/0...hange-00094670

Given their druthers, the FAA would really prefer Congress pass. A law explicitly directing them on this.