The purpose of the 10th Amendment is to draw a line between the federal and state government's powers. This amendment also protects their powers from each other. This amendment has been used to define the federal government's power to tax, law enforcement and federal regulations. At one point in time this amendment was easily interpreted if it's not included in the constitution, the federal government cannot give it to the states. Over the years federal power was expanded through cases in the Supreme Court.
When the founding fathers wrote the Constitution, they encompassed the 10th amendment, which says "The powers delegated to the United States by the constitution, nor prohibited by it to the states, are reserved to the states respectively, of the people." The problem with this statement is that it can be interpreted in different ways.
The powers of the National government are usually the powers of congress, because they make the laws.
The power of congress came from Article VI which states that the constitution is the "supreme law of the land" This means that the states must follow the constitution even if it conflicts with the state laws. The national constitution has jurisdiction over all state constitutions. The constitution mentions very little about states' rights so it can be hard sometimes to see the thin line between the national and states powers. The court has sometimes had to decide the exact interpretations of the tenth amendment to distinguish national and state power.
In the year 1978 Congress passed the Alien and Sedition Acts which outlawed "any false, scandalous writing against the government of the United States. Thomas Jefferson and James Madison believed that congress didn't have this authority so they drafted the Kentucky and Virginia Resolution. They believed that the federal government had no right...