Citizen initiatives and popular referenda are two forms of direct democracy.  The citizen initiative process enables citizens to bypass their state legislature by placing proposed statutes and, in some states, constitutional amendments on the ballot. Twenty-four states have citizen initiative processes. The popular referendum process allows voters to approve or repeal an act of the legislature. Twenty-three states have popular referendum processes.

In 2002, the National Council of State Legislatures published Initiative and Referendum in the 21st Century, an in-depth study on initiatives and referenda that includes recommendations for policymakers.  Their Citizens Initiatives and Popular Referendums Database allows you to search by topic and find state specific information.