If you have to call a foul, it would be a nonplayer foul with a succeeding spot enforcement. but if this is media and not a member of the team/coaches/support staff, I wouldn't throw a flag. I would ask game administration to remove the person from the sideline.
NFHS 10-4-5-a identifies the enforcement spot for USC fouls as the
succeeding spot. As for media, or other individuals not under direct team supervision, Game Mgmt/Security would be the appropriate reference. In the event of non-compliance, or delayed response, keeping the Game Clock stopped pending full compliance may prove helpful and such behavior should be included in the game report.
This can be of particular concern when play originates within close proximity to (on both sides of) a goal line, impacting the necessary operating space of field officials.