The mayor sent letters to about a dozen businesses in Indiana. The letter cites Indiana's Religious Freedom Restoration Act.
Indiana Gov. Mike Pence signed the measure last week and defended it during a television appearance Sunday. The act prohibits state laws that "substantially burden" a person's ability to follow his or her religious beliefs.
In the letter, Emanuel says the act is wrong and urges Indiana business owners to "consider Chicago as a place to move and grow." Emanuel writes that businesses can't "succeed in the global economy if you discriminate against your residents."