What do "constitutional" and "unconstitutional" really mean in the US?

Question

People in the US often talk about how some laws, decisions, ruling, executive orders are "unconstitutional", but what does that word mean?

Does "constitutional" mean "obeying only the Constitution", or does it expand to "exceptions under constitutional laws", too?

For example, if A says B is an evil person and should die, is it A's constitutional right to say whatever they want, under the First Amendment, without being suppressed by the government? Or is it exempted from constitutional protection because it is "insulting" or "fighting words" according to Chaplinsky v. New Hampshire, and therefore A should be punished with civil remedies? What if, as a result of what A says, C, a die-hard fan of A, goes out and tries to assault B? Would A be criminally liable too?

Answer 1

Usually these words refer to whether something (e.g. a law or government action) is or is not in accordance with the Constitution, including its amendments, as currently interpreted by US courts including the Supreme Court.

So in view of Chaplinsky, the Constitution (as interpreted) does not protect "fighting words", and therefore a law that forbids "fighting words" is constitutional.

As phoog points out in the comments, the word can also be used to refer to whether something is in accordance with the Constitution, as the speaker thinks it ought to be interpreted. So somebody might say that a certain law or action is (un)constitutional, even if a court has not considered it, if their own personal interpretation of the Constitution is (or isn't) consistent with it. Or, if a court has struck it down (or upheld it) but the speaker thinks they erred in doing so.

Answer 2

An act is "unconstitutional" if it is not permitted by the Constitution. Everything else is "constitutional." The only way to know whether a law is constitutional is for the U.S. Supreme Court to addresses it; until then, most discussions of constitutionality are purely opinion.

But because the Constitution is almost exclusively limited to rules about the government, we would rarely describe something as "constitutional" or "unconstitutional" unless it was an action taken by the government. Private conduct rarely implicates the constitution, so asking whether it is "constitutional" is about as useful as asking whether your pool was built in compliance with the Hippocratic Oath.

For example, if the government imposed a new restriction on abortion, we would debate whether it was constitutional or unconstitutional. But if a woman obtained an abortion -- even in violation of that new restriction -- no one would talk whether the abortion was constitutional or unconstitutional.

To your example, then, laws restricting speech are generally unconstitutional, but there are exceptions (e.g., restrictions on fighting words) that are constitutional. So the law itself would be constitutional, but regardless of what the law is, saying that someone is evil would not be described as constitutional or unconstitutional.