Code of Federal Regulations Title 29. Labor § 29.35.13 Exceptions to the rules against age discrimination:  reasonable factors other than age

A recipient is permitted to take an action otherwise prohibited by § 35.10, if that action is based on a factor other than age, even though the action may have a disproportionate effect on persons of different ages. An action is based on a factor other than age only if the factor bears a direct and substantial relationship to the normal operation of the program or activity or to the achievement of a statutory objective.