> If federal laws are above state laws, then what's the point of state laws?

I'll try for an on-topic reply this time instead of US history lesson. The way the system's intended to work is that each state regulates matters that are strictly internal to itself, and the federal government is just responsible for laws about how multiple states interact / trade with each other, and how the US deals with other countries in diplomatic or military matters. This was how it actually originally worked with the thirteen original states who viewed themselves as independent countries in a relatively loose military / economic alliance (as opposed to the modern view of states as more like large administrative districts in a single nation).

Due to all of the history I mentioned in my other comment, plus changing culture, plus the changing domestic / world economy resulting in lots more trade with faraway places, plus the expansive interpretation of the commerce clause [1], led to there being more and more things which at least touch on "interstate matters" or "foreign trade" or "foreign policy" and belong to the federal government, and less and less things that are strictly "intrastate matters" for the state government to deal with.

States still have plenty to do. First, local governments have no Constitutional authority, so city and county governments are set up by states [2]. Next, maintaining lots of roads / bridges / infrastructure, setting up laws against street crimes like shoplifting, assault, murder, etc. and maintaining police / courts / prisons to deal with them, and much of the education system are largely state responsibilities. Also, the non-criminal law system (e.g. lawsuits) is handled within the state [3].

States have their own military forces (referred to as "militia" in the Constitution, but usually called "National Guard" today) which largely consist of part-time soldiers and whose activities in modern times are mostly training and local disaster relief, but also function as reserve forces for national military activities including overseas wars [4]. States also run elections, register and regulate businesses, license and regulate various activities such as medical practice, regulate lotteries and casino gambling, and fund state universities. The federal government often offers to share some of these responsibilities, or attempts to get the state to voluntarily delegate some of its authority to the federal government (for example, a common tactic is offering federal funding for state projects, but requiring states to comply with federal rules for the use of the funds to be eligible to receive them).

[1] http://en.wikipedia.org/wiki/Wickard_v._Filburn

[2] The nation's capital, Washington, D.C., is considered not to be a part of any state, and authority for its government rests with Congress. (For the past forty years, the city's elected a mayor and city council, who do most of the actual local governing.) A continual sore point with the capital's residents is that, ironically, they have no voting representative in Congress! http://en.wikipedia.org/wiki/Washington,_D.c.

[3] Non-criminal law is called "civil law" http://en.wikipedia.org/wiki/Civil_law_(common_law) Unfortunately, the term "civil law" can also refer to the completely different concept of a legal system which is descended from Roman law. The US state of Louisiana is a former French territory and has a legal system based on civil law; the rest of the United States' legal system is based on English law (referred to as "common law"). http://en.wikipedia.org/wiki/Common_law http://en.wikipedia.org/wiki/Louisiana#Civil_law

Also, there are some non-criminal cases that can exist in federal court, for example, suing a party from a different state, or questioning the constitutionality of a law; see http://www.uscourts.gov/FederalCourts/UnderstandingtheFedera...

Of course, the Supreme Court is the highest level of appeal for all cases in both federal and state courts.

[4] http://en.wikipedia.org/wiki/National_Guard_(United_States)#...