By setting up a national policy, the system is fair to everyone and the states do not have to bear the heavy burden of regulating their currency. On the other hand, issues such as the death penalty have been lift up to the individual states. Where to have death penalty depends on the history of the state and needs and philosophies.
The supreme law of land only for United States and its citizens. It is called supreme because all other sub forms of government within the country and all legislation passed by individual states and their local government cannot pass laws that displace the rights and laws of the federal government. The Federal government job is to give and protects the right of all citizens their right which cannot be trespassed by any other legislation who interrupt these right. The Supreme laws protect the fundament rights of the constitution created for the citizens of the United