The Selective Service System is the federal agency tasked with collecting and maintaining information on those who may at some point be subject to a draft, or military conscription. Under U.S. law, if you’re male (as assigned at birth) and a U.S. citizen or immigrant non-citizen, you are legally required to register with the Selective Service System within 30 days of your 18th birthday.
Of course, the government hasn’t actually had a draft in place since the 1970s, during the Vietnam War. And not since the 1980s, after Jimmy Carter reestablished registration in his last year in office, has it prosecuted anyone for not registering — a move that proved widely unpopular.
Aside from being a form of extortion and an affront to individual rights, draft registration is part of a system destroying human life. Resistance should be seen as part of a broader movement for survival of the planet.