Likely no one.
Really.
Tell that to the 5 guys in San Antonio that were sued back around 2009 when (in 2004) one of them, quite properly, was covering a play from the restricted area and, while running virtually full-speed, collided with an assistant coach that had stepped into the restricted area. Both were knocked unconscious. The official fully recovered, but the coach suffered brain injuries that forced him to leave coaching, and, some years later, contributed to his death. The coach's insurance company sued on the argument that the coach had not been warned to stay out the restricted area. Ultimately, the officials were given a summary judgment, effectively absolving them of any responsibility. Duh. By RULE, the restricted area is called the restricted area for a reason, and, again, by RULE (which coaches are supposed to know), is supposed to be kept clear while the ball is in play. But, that won't keep some folks, especially media and lawyers, from attempting to vilify officials over such incidents (not to mention on-field rulings that, in their minds, affect the outcome of a game).
Keep 'em off the field, and out of the restricted area.