Re: Eugene on US law:
"As I already admitted, my knowledge of these things in the US is not deep, despite having lived here for [redacted] years. In any case, my impression is that some federal (US) laws are enforced by the federal government with their own criminal justice departments (mainly FBI) and federal courts. Other federal laws might be expected to be enforced by the individual states using their own criminal justice systems. But in the end, whether or not the individual states choose to enforce the federal laws is effectively up to them. In some cases a state might choose to go in a different direction and write laws that contradict federal laws. I don't know if this is specifically allowed by federal legislation (I doubt it) but the federal government typically doesn't pursue these matters legally.
The consequence (as I see it) is that federal laws in the US are meaningful only if individual states no not choose to explicitly over ride them with state laws."
In normal US constitutional law, as I understand it, there are Federal statutes (against espionage, for example) and State statutes (against murder, for example).
There are some Federal statutes, such as against murdering a President, that overlap State statutes.
However, Federal laws and the US Constitution override State law when they conflict.
Most "normal" crimes, such as assault, homicide, burglary, sexual assault, etc. are State crimes, which vary from State to State in definition and punishment.
Not all states have capital punishment, for example, but all outlaw murder (though the terms applied to the crime vary from State to State on their lawbooks.)
A specific statute (Federal or State) can be ruled unconstitutional by the Supreme Court.
The power of the Supreme Court to overrule legislation was established by the early decision: Marbury v. Madison (1803), where Madison was US Secretary of State at the time of the ruling.
Note that this power is not explicitly mentioned in the Constitution, but was held by the Court to be inherent therein.
Stare decisis!.