All states are governed by the U.S. Constitution. Additionally, each state has its own state constitution. State constitutions can provide additional protections and rights not found in federal law; however, they cannot deprive a state's residents of their federal constitutional rights.
Iowa's current constitution has been amended 46 times since its creation. The process to amend the Iowa Constitution is the following:
Legislation must be passed by both the Iowa House and the Iowa Senate within the period of one General Assembly—which is two legislative sessions.
The same legislation must again pass both houses by the end of a second, consecutive General Assembly.
The issue is then put in front of the voters. The congressional amendment must win the approval of a majority of voters.