You need a really good reason to order a credit check on a candidate for employment (among them - if they handle cash, or need to be bonded). Otherwise, there generally is no good reason for doing it. There is no evidence that a person with poor credit is going to be a poor employee.
Ask yourself - what is the business justification for doing it? People are starting to fight back against this practice, and you could find yourself explaining to a judge why you declined a qualified candidate because they missed a credit card payment a few years ago.