Yes. Only the captain can approach the referee or, if the captain is a goal keeper, a nominated player.
Trying to stop the surrounding of refs and yellow cards are supposed to be issued against players that break the rule.
I saw Porteous tried his best to mouth off yesterday despite the fact the ref was talking to Robertson.
Should have just walked off with his head down after such a horror tackle, maximum amount of winding neck in required after letting his side down that hard.