Intentional or not, this is an Unsporstmanlike Conduct foul for an Unfair Act. The referee may take any action he deems equitable. IMHO, at a minimum, this would be a 15 yard penalty. Since the penalty statement references the possibility of ordering the down to be repeated, that would also mean that the referee could impose a Loss of Down.
In this case, I would impose a 15-yard penalty from the previous spot with a loss of down. That should motivate Team A to keep their sideline under control.
The previous sideline warning would be irrelevant, unless the squad member was in the restricted area or on the field. But, as we have been directed, once a team gets a 15 yard penalty for Game Administration and Sideline interference, every violation thereafter will be 15 yards, regardless of how many, or how few, previous sideline warnings/penalties they have committed. So, I would consider this foul as justification to go directly to 15 yard penalties for any/all future violations.
