[ANSWERED]Is it legal to do cross-realm ingame gold trade?

[Chrysamere]

I need gold on outland, i have gold on Icecrown to trade for it.
Its considered safe as people can trade in small amounts to avoid scam for bigger amounts.
Can I tell to people on Outland channels/towns that : "WTT gold here vs gold on Icecrown" ?
Or if not, is there some exact rule somewhere about this?
Ppl do this sometimes either way i'm just asking if there's anythong problem with it? everything happens ingame
Thank you for answer!

[Borrean]

It is allowed but not recommended.