I wouldn't think "anybody" would need a federal mandate for permission to salute our flag.
Many Law Enforcement officers have done this for decades. ??
The military has strict rules for behavior in vs out of uniform. Failure to follow those rules could result in disciplinary action. If I recall correctly, until this change salutes were only to be rendered when in uniform; when out of uniform one covered ones heart with one's hand.
Law enforcement is completely different, they are not subject to military rules and regulations.