ST. LOUIS, Aug. 28 (Thomson Reuters Accelus) - Major banks are getting increasingly wary of some transactions with smaller banks that have begun to allow marijuana businesses to open accounts. Officials at the bigger institutions say they fear being in breach of anti-money laundering laws and are pressing federal authorities to make it clear what is legitimate and what is illegal.The problem arises because in Colorado and Washington states, marijuana for general use is legal, and in a host of other states it is legal for certain medicinal purposes.