In this instance, according to Melissa Sorenson, executive director of the National Association of Professional Background Screeners, federal regulations do not supersede state or municipality regulations, and that can lead to the need to respond to a wide variety of requirements.

In the SHRM report, Sorenson says, "Ban-the-box legislation often involves variances with specific letters, language, wait times and more that require employers to have different processes in different jurisdictions and treat applicants differently based on their location."

With 24 states and more than 150 cities and counties currently having such laws in force, which require hiring managers to delay asking about a candidate's criminal history until after an interview has been conducted or a provisional job offer has been extended, experts believe that such laws will "become the norm."

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Montserrat Miller, a partner in the Washington, D.C., office of Arnall Golden Gregory, said in the report that "[c]ivil rights groups and others view ban-the-box initiatives as important toward re-entry efforts by ex-offenders, the argument being that these measures reduce unfair barriers to employment for those with criminal records."

Another challenge employers face is how to screen the contingent workers of the gig economy. The report cites a 2015 American Action Forum report estimating that gig workers account for 30 percent of new jobs, and a report from business and financial software company Intuit that estimated gig work would grow by 18.5 percent per year over the next five years.

But companies aren't clear on how to screen gig workers. Some states have passed laws requiring background checks for such workers as Lyft or Uber drivers, while many companies have skipped background checks on the rationalization that such workers are not employees.

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Sorenson says in the report, "Over the past couple of years, that philosophy has changed, with a realization that whether the individual is an employee, independent contractor or otherwise, the worker represents the employer's brand, and screening — particularly when access to people or sensitive material is involved — is a critical risk mitigation tool, regardless of the worker's classification."