Legality of referral fees

[Jason Bentley]

If a bankruptcy attorney (trustee) refers one of his/her clients to me because I can buy their house quickly and then I close on the house, is it legal for me to pay the referring attorney a referral fee for the lead?

Do you know the written law concerning this? Or how I could look it up? Could it vary from state to state? It sounds silly that I wouldn't just ask the attorney but I could take a guess as to what they might say...