Macros usage in game

Whats the rules on macro usage in game? What I mean by this is macroing your skills together. An example would be katarina macroing e into w into r so all she has to do is hit 2 keys (q and whatever the macro key is).

I am wondering cause I just got out of a game where it was openly admitted that she was macroing. I don't do it and won't do it. I think if you can't play the champ without the help of a scrub macro then you just shouldn't play the champ. I was just wanting to know the rules on it.