It is. 17 U.S. Code § 1201 - Circumvention of copyright protection systems
Rooting/jailbreaking have had exemptions for many years now, on a three year basis which has seemingly been continually renewed, by the Librarian of Congress.
Exemption to Prohibition on Circumvention of Copyright Protection Systems for Access Control Technologies (2024)
https://www.federalregister.gov/documents/2024/10/28/2024-24...
He wasn’t convicted, so that’s not been proved to be against the law in this case, so it doesn’t support the argument you’re advancing in this thread.