Final Answer:
The employee would not have an affirmative defense under the ADA by claiming a physical condition led to the drug use in the case of termination for unauthorized substance use.
Step-by-step explanation:
The Americans with Disabilities Act (ADA) prohibits discrimination against qualified individuals with disabilities but doesn't protect individuals engaged in current illegal drug use. While the ADA does offer protection to individuals with past substance abuse issues who are no longer using illegal drugs and have undergone rehabilitation, it doesn't shield employees engaged in current illegal drug use.
In this scenario, if an employee is terminated for unauthorized use of a controlled substance, claiming a physical condition led to the drug use wouldn't constitute an affirmative defense under the ADA. The ADA doesn't protect individuals engaging in current illegal drug use, regardless of whether the drug use stems from a physical condition or not.
Affirmative defenses under the ADA usually involve accommodations for individuals with disabilities to perform essential job functions. However, when it comes to illegal drug use, the ADA's protections are limited.
Therefore, in this situation, the employee wouldn't have an affirmative defense under the ADA based on a claim that a physical condition led to the drug use.