[Excerpt] Federal, state and local governments can each pass laws in the United States. When a city passes local laws–like noise ordinances–it can do so without involving the federal government. However, it cannot pass laws that contradict federal law or jurisdiction. So, as federal laws change, they shift what states and cities can or cannot do. State or local governments prepare for this by drafting laws that automatically go into effect once federal law changes. These are called Trigger laws.