TOS can't violate existing laws.  For example I can't put in a TOS by using the service you agree to transfer all property to xyz corp and then go into court and say "see he agreed give me the deed to his house".  A company can refuse to do business but they can't refuse to do business and "hang on to" another persons assets.  The honest and clear thing to do would be for the service provider to have client complete any requirements first and then accept funds. For example if the service provider is worried about ACH fraud they could send a random small amount of funds to the clients account to verify it.  If they need any docs they can design the site such that the client can't send funds until verified.  

Nothing in MSB regulations requires or even allows a company to just keep client funds.  The purpose of AML is to prevent the TRANSFER of suspicious funds not to deprive criminals of (note not saying the OP just pointing out the purpose of AML programs is to prevent not seize).  Seizure of assets is a law enforcement activity pursuant to a warrant by a judge.  The company has no authority to seize funds of clients under any circumstances.  If funds are returned then there is no transfer. In the event of a "suspicious transaction" the proper procedure is to file a SAR with FinCEN.  If the company had completed mandatory AML training and had a written AML compliance program as required by a MSB they would already know the proper response.  Companies doing stupid shit like seizing the property of another person is why money transmission is so heavily regulated at the state level.  State regulation and licensing has nothing to do with AML, it is about protecting clients from illegal actions of companies.

I mean you are a logic person obviously if that was the case that a company could just keep funds based on vague terms of service it would be a good way to turn a profit doing nothing.  Sorry before we can complete this transactions we need a copy of your DL ... now we also need a copy of your utility bill ... sorry we also need three personal references ... sorry we need your SSN and written permission to access your credit report .... sorry we also need a notarized copy of your high school diploma ...

http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=017335056cf96e754794b9fe7336e17c&rgn=div5&view=text&node=31:3.1.6.1.6&idno=31#31:3.1.6.1.6.3.5.8