Supreme Court :)
The appropriate Court of Appeals ( ie: US District Court of Appeals)
what is the ruling of a country,state,or district
In the Federal court system, the district courts are the "lowest" courts. Cases usually start in district court and are decided there. The circuit courts are courts of appeal. That means that you can appeal a district court's ruling to the circuit court (and then to the Supreme Court, if you still don't like the ruling). In that sense, the circuit courts are "higher" than the district courts.
A United States Supreme Court decision is mandatory on all lower federal courts. That includes federal courts of appeal and federal district courts.
Magistrate
You should discuss this with an attorney. You would file the lawsuit in a Federal District Court; the process is quite complicated and you will benefit greatly from being represented by a competent lawyer.
On State Courts of Appeal - their rulings are binding on the entire states court system. On the findings of a Federal Appeals Court - they are binding upon the federal district courts within THAT appeals courts circuit.
The federal ruling system is considered more democratic because of the division of power, and the various checks and balances put in place.
Federal ruling systems are more democratic and inclusive than unitary ruling systems because the government remains close to its people, encourages devolution of government resources, and bars dominance of the majority.
None, Japan was never a Federation.
Gerrymandering
An interpretation of the second Amendment that corresponds with the ruling in District of Columbia vs. Heller is that citizens have the right to keep and bear arms.