The protesters are citizens, and they're complaining about a new law that was just passed. What should they do if they want to challenge the law? *
Write to the mayor
Write to the president
Use the town council
Use the court system

Use the court system

Explanation:

In order to challenge a new law as a citizen you need to use the court system.   The citizen in question would need to file a class action lawsuit in court seeking to declare the federal law unconstitutional. This is then reviewed and decided by the courts, where the Supreme Court ultimately has the final verdict on this issue.