Albertson's, Inc. v. Kirkingburg
In Albertson's, Inc. v. Kirkingburg, 527 U.S. 555, 119 S.Ct. 2162, 144 L.Ed.2d 518 (1999), the Court upheld an employer's right to refuse to employ an ADA plaintiff for his failure to meet a generally applicable federal minimum vision regulation, despite the fact that the plaintiff had obtained permission to participate in an experimental federal vision-safety program that would not have disqualified him for his poor vision.
The Court explained:
The waiver program in which the plaintiff would participate was simply an experiment with safety, however well intended, resting on a hypothesis whose confirmation or refutation in practice would provide a factual basis for considering the existing standards.... It is simply not credible that Congress enacted the ADA (before there was any waiver program) with the understanding that employers choosing to respect the Government's sole substantive visual acuity regulation in the face of an experimental waiver might be burdened with an obligation to defend the regulation's application according to its own terms. Id. at 576-78.