The United States Constitution grants states the right to make their own laws. However, state laws cannot contradict federal law.
Understanding the Relationship Between State and Federal Law
The U.S. Constitution was written so that states have a level of autonomy and could govern themselves. However, there are certain matters the federal government deems so important that they are covered by federal law. Federal law will always supersede state law, according to the supremacy clause in the U.S. Constitution.
The Authority of the Federal Government
There are certain crimes that are exclusively covered by federal law. One example of this is the counterfeiting of money. It is the federal government that dictates what currency can be used, and it is also the federal government that prosecutes individuals who create fake currency. One could easily imagine the chaos that would ensue if every single state had the power to make and to regulate their own money.
The federal government has authority over things like interstate business, US mail, air traffic, and trucking. So if a person decides to put graffiti on a building, it is a local crime. However, if that same person chooses to graffiti the US Post Office, then it is a federal crime because the crime was committed against an entity that is under the jurisdiction of the federal government. The defendant in this type of case would require a federal criminal defense attorney to help them. Any part of the law that is not governed by the federal government is under the jurisdiction of the state.
When a Crime Goes From Being a State Crime to a Federal One
On the other side of the coin, imagine that an individual is driving while under the influence of alcohol, crosses the border from Minnesota to Wisconsin and is arrested. His crime does not become a federal offense simply because he crossed a state border. It is still a state offense that will be handled by the state of Wisconsin because this individual’s crossing state lines posed no national security risk. However, if that same individual crossed the Minnesota/Wisconsin border after having kidnapped someone, then their crossing state lines is considered a national risk, and their crime goes from being a state matter to being something that is dealt with on the federal level.