Does the phrase "during a national emergency" in 10 U.S.C. § 101(a)(13)(B) entitle federal civilian employee reservists to differential pay based on mere temporal coincidence. Specifically, it addresses whether a reservist must prove a "substantive connection" between their active-duty service and a particular declared national emergency. The Court must determine if the statutory language requires this relational link or only that an emergency be ongoing during the period of service.

• Argues that 5 U.S.C. § 5538(a) and 10 U.S.C. § 101(a)(13)(B) entitle him to differential pay because he was ordered to active duty under "any other provision of law" (specifically 10 U.S.C. § 12301(d)) while a national emergency existed.
• Contends that the phrase "during a national emergency" should be interpreted according to its ordinary meaning as a temporal requirement.
• Asserts that he does not need to show a substantive link between his specific duties and the declared emergency to qualify for payment.

• Argues that "during a national emergency" requires a reservist to demonstrate a "substantive connection" between their service and a particular national emergency.
• Contends that a purely temporal reading would render the phrase superfluous because national emergencies are almost perpetually in effect.
• Asserts that interpreting the statute as merely temporal would lead to anomalous policy results, such as providing differential pay for reservists attending training or facing court-martial.

• The Court held that a federal civilian employee is entitled to differential pay if their service "temporally coincides with a declared national emergency" without needing to show a substantive connection.
• Relying on *United States v. Ressam*, the Court reasoned that the word "during" normally denotes a temporal link meaning "contemporaneous with."
• The Court noted that when Congress intends both temporal and substantive connections, it uses explicit phrases such as "during and in relation to" (e.g., 18 U.S.C. § 924(c)(1)(A)) or "during and because of" (e.g., 5 U.S.C. § 6323(b)(2)(B)), citing *Ysleta del Sur Pueblo v. Texas*.
• The Court observed that 10 U.S.C. § 12302 uses the phrase "[i]n time of national emergency," which the government conceded is purely temporal, making it implausible that "during a national emergency" in § 101(a)(13)(B) would require more.
• The Court found that requiring a substantive connection would create interpretive difficulties because the statute provides no principled way to determine what kind of connection suffices.
• The Court reasoned that a substantive requirement would create tension with 18 U.S.C. § 209, as it would be unclear to private employers when providing differential pay becomes a federal crime.
• The Court pointed to Congressional Budget Office (CBO) cost estimates for similar legislation, which calculated costs based on the "total number of reservists on active duty" rather than those in emergency-related duties.
• The Court rejected the surplusage argument by noting that the National Emergencies Act shows emergencies are not immutable and that a temporal link is still meaningful because such service bolsters the government's overall capacity to address an emergency.
• Regarding policy concerns, the Court cited *Epic Systems Corp. v. Lewis* and *Patel v. Garland* to conclude that potential anomalous consequences cannot trump the best interpretation of the statutory text.