How Far is Too Far on The Field?

[grunewar]

I was watching an NFL game today and saw one of the coaches run onto the field a good 15/20 yards. This is not of course just an NFL issue as I see it weekly in college too as coaches go berserk over calls or to get an officials attention - haven't really see it when I go to HS games.

My question is this - how far is a coach "allowed" on the field or "down the field" as they run onto the field and not just at mid-field? Does it differ for Pro, NCAA, Fed?

I understand the restricted nature of the sidelines and the likes and have seen calls where officials penalize teams for coaches and players violating restrictions.

Just curious as to the rule and what you, as football officials do - requests not to do it, warnings, flags? (I don't do this sport, just curious as I see it a lot).

Thanks