President George H.W. Bush signed the Americans with Disabilities Act into law nearly 30 years ago, yet there are still several aspects of the law that remain unclear and ultimately need to be resolved by the U.S. Supreme Court.

Areas of the law that that lack clarity in the workplace involve long-term leave to accommodate employees with disabilities, competition between disabled and non-disabled candidates, and whether attendance is an essential function of a job. That lack of clarity can land employers in court, which can be costly, even if they ultimately prevail.

Recent examples of companies defending against ADA claims...