Employers in Maine will be prohibited from asking prospective job candidates about their previous criminal histories under a new law signed by Gov. Janet Mills. The new law, which was approved by the Legislature in the final days of its session, will ban companies from screening people with criminal backgrounds before those applicants have an opportunity to go through the preliminary hiring process. Under the new rules, which take effect in October, employers must delay questions about criminal history until after they’ve made a conditional offer of employment. After that, they can ask about criminal convictions, but not about previous arrests or charges. There are also exemptions in the new law for situations where a previous felony conviction prohibits a prospective employee from being considered for the opening. Employers that violate the new rules, which will be enforced by the Maine Department of Labor, could face penalties of up to …