MiRoto: there are some legal eagles on this board, but I'm not one of them.  I'll try to answer in layman terms:  P411 is just a screening service--they verify the identities of providers and the identities & employment of clients.  P411 allows two parties to exchange information, that's all.  

LE would need a warrant to gain access to P411 data, but what would they base their warrant on?  Let's pretend they got a warrant based on 'conspiracy to aid in prostitution'  (ugh!)  

If my name or yours is in the P411 database--what crime have we committed?  There are some providers in that database who don't offer FS.  And there are clients in that database who aren't looking for sex but merely companionship.  For LE, I don't know how they could make a case here. --z