Many of the federal courts do not like the broad reach of the ADA and have attempted to limit it by a restricted reading of what constitutes a major life activity. The regulations to the Rehabilitation Act, which also govern this aspect of the ADA, are ambiguous: "Major life activities" means functions such as caring for one's self, performing manual tasks, walking, seeing, hearing, speaking, breathing, learning, and working. Some courts take this literally, finding that activities that are not on the list, such as reproduction, are not major life activities.

The U.S. Supreme Court first ruled on the definition of major life activity in Bragdon v. Abbott. Plaintiff was a patient with HIV who claimed she was discriminated against by a dentist because he wanted to do her dental work in an operating room to better manage the risk of spreading HIV to the dental personnel. The defendant claimed that HIV was not a disability because the patient was asymptomatic and thus there was no affect on any of her major life activities.