Has he registered for selective service, or does he have those pesky genetic bone spurs that allow you to play football, baseball, soccer, and wrestling while attending military school, but prevent you from actual military service?
Most people in the US get automatically registered by their state DMV to the feds, but you’re technically responsible for doing it even if you don’t get a driver’s license
It's a "draft" sign up everyone signs when they register to vote or get thier drivers license. Since there's no longer a draft it's basically just saying yes to maybe being selected for jury duty someday.