Just stay clear of banning religious dress that doesn’t pose a safety hazard—that might amount to religious discrimination. On the other hand, as the following case shows, you don’t have to allow the same employee to sport the religious (and other) symbols of multiple faiths.
Recent case: Wal-Mart cashier Daniel Lorenz dressed within societal norms for the first few months on the job. Then he began wearing a priest’s collar and shirt. Soon, he began adding a beret or court jester’s hat. Then it was a Muslim kaffiyeh, multiple crosses, plus anarchy and peace symbols.
called Lorenz aside and explained the company’s dress policy. Lorenz could wear the headdress but not the priestly garb or other assorted symbols. He continued the masquerade and was fired. He filed his own lawsuit (presumably unable to find a lawyer to take his case). When the trial court dismissed his case, he appealed to the 5th Circuit Court of Appeals.
That court also threw out the case. While employers have to reasonably accommodate sincerely held religious beliefs, this clearly went beyond the requirement. (Lorenz v. Wal-Mart, No. 06-51024, 5th Cir., 2007)