<Li> Military participation is not currently required in the United States, but a policy of conscription of men has been in place at various times (both in war and in peace) in American history, most recently during the Vietnam War . Currently, the United States Armed Forces are a professional all - volunteer force, although both male U.S. citizens and male non-citizen permanent residents are required to register with the Selective Service System and may be called up in the event of a future draft . Johns Hopkins University political scientist Benjamin Ginsberg writes, "The professional military has limited the need for citizen soldiers ." </Li> <Li> Taxes . In the United States today, everyone except those whose income is derived from tax - exempt revenue (Subchapter N, Section 861 of the U.S. Tax Code) is required to file a federal income tax return . American citizens are subject to federal income tax on worldwide income regardless of their country of residence . </Li> <Li> Support and defend the Constitution against all enemies, foreign and domestic . The Constitution establishes the U.S. system of representative democracy and outlines the inherent principles of freedom, liberty, and opportunity to which all citizens are entitled . The continuity of this Nation's unique freedoms depends on the support of its citizens . When the Constitution and its ideals are challenged, citizens must defend these principles against all adversaries . </Li> <Li> Stay informed of the issues affecting your community . U.S. citizens should learn about the issues and candidates running for office before casting a vote in an election . Staying informed allows citizens the opportunity to keep the candidates and laws responsive to the needs of the local community . </Li>

In some states citizens can vote directly on matters of public policy through