A federal statute requires retirement at age 75 for civil service employees, but age 65 for armed forces civil service employees. A 65-year-old federal employee seeks to block retirement at 65. The strongest argument is that the law:

• A. denies him a privilege or immunity of national citizenship
• B. deprives him of a property right without just compensation
• C. is not within the scope of any enumerated powers of Congress in Article I, Section 8
• D. invidiously discriminates on the basis of age in violation of the Fifth Amendment

Answer: (D)

Equal protection applies to the federal government through the Fifth Amendment. The rule here treats people differently based on age: civil service employees must retire at 75, while armed forces civil service employees retire at 65. That creates an age-based classification that isn’t tied to a clear, legitimate objective for one group over the other. In constitutional terms, a law that uses age as the sole basis for a retirement cutoff invites an invalid classification unless a strong rational basis is shown; without a solid, service-related justification, the distinction is an invidious form of age discrimination under the Fifth Amendment.

The other options miss the central issue. It isn’t about citizenship privileges, a taking of property, or a lack of Congressional power—the law regulates retirement ages, which Congress can do, and the claim isn’t about a property interest or a constitutional limit on Congress’s powers. The strongest challenge rests on the age-based discrimination argument under the Fifth Amendment.