There has been some labor rulings which, in effect, create a sorta kinda co-employment situation between clients and temps that are supervised directly by clients. In general, it is not a good idea for Clients to allow temps to work directly for them for a year or more continuously.

If a temp works for and is directly supervised by a Client for a year, that temp has some legal grounds to argue either that he is "in effect" a full time employee of the Client and or that he is legally entitled to either full time benefits or to join the labor Union the Client's employees are in.

When temps are supervised by temps, it may help to prevent the creation of a co-employment situation. Also, in an outsourcing situation, since the workers are not supervised by the Client's staff, a co-employment situation may not apply.

All in all, there is liability to Employers associated with having employees and liability to Employers sassociated with their supervising temps directly.