In recent years there have been a variety of laws that restrict employers during the hiring process.  Some of those restrictions include:

• "Ban the box” laws may restrict you from asking questions regarding an applicant’s criminal history. These laws are designed to secure jobs for more people by either delaying the point in time you can ask an applicant about their criminal past, or prohibiting you from asking altogether. Many states and cities and counties now have such laws.
• Some jurisdictions prohibit employers from asking about an applicant's wage history. If your applications ask about criminal history in these jurisdictions, you should remove that from your application.
• You must obtain an applicant’s written authorization before having a third party run a search on the applicant’s criminal or motor vehicle background. The Fair Credit Reporting Act requires that authorizations must be on a standalone document that contains a clear and conspicuous disclosure and cannot include additional requirements not permitted under the law.

These are just a few of the many restrictions on employers during the hiring process.  You should be mindful of the many federal, state and local laws that restrict employers during the hiring process.