Supplementary card from away course and who can mark it?

[rulefan]

That in bold really is a laughable statement. As a marker you can have a suspicion however unless you can prove anything you cannot do a thing. I would suspect that every golfer the world over that witnesses an infringement of the rules will pull that person up there and then in order to rectify/clarify the position.

I did use the word 'allow' as a deliberate action. If you know the player is cheating and take no action, that is cheating and in breach of the rules.