The constitution of the United States grants certain rights to the federal government and to the state government. Both the federal and state governments can make laws. Any laws made by a state will be binding on their territory under its jurisdiction while federal laws bind all states. unless there is a state law that directly contradicts the federal law. When laws begin contradicting the supremacy clause comes in.
The Supremacy Clause is found in the second paragraph of Article VI of the constitution. It states the United States Constitution is the highest law of the country and that all state and federal officers and judges have to uphold the Constitution and all of its rules. The clause gives federal laws the upper hand