It may be a defense to a charge of discrimination under the ADA that a challenged action is required by another Federal law or regulation, or that another Federal law prohibits an action that otherwise would be required by the ADA. This defense is not valid, however, if the Federal standard does not require the discriminatory action, or if there is a way that an employer can comply with both legal requirements.
ADA requirements supersede any conflicting state workers' compensation laws.
For example: Some state workers' compensation statutes make an employer liable for paying additional benefits if an injury occurs because the employer assigned a person to a position likely to jeopardize the person's health or safety, or exacerbate an earlier workers' compensation injury. Some of these laws may permit or require an employer to exclude a disabled individual from employment in cases where the ADA would not permit such exclusion. In these cases, the ADA takes precedence over the state law. An employer could not assert, as a valid defense to a charge of discrimination, that it failed to hire or return to work an individual with a disability because doing so would violate a state workers' compensation law that required exclusion of this individual.