In the US, a court typically can only review a law if a case is brought, which generally requires a plaintiff with standing to sue. I seem to recall that some other country or countries have a system allowing for judicial review of laws/bills without waiting for such a case to be brought. What countries, jurisdictions, or legal systems allow for such preemptive review? What are the advantages and disadvantages?
In Canada at least the Government can ask the Supreme Court for its opinion on the constitutionality of any legisation - often before the legislation is adopted. This is called a Reference to the Supreme Court, and has been used several times - most recently to establish the constitutional requirements for Senate reform.
Germany has the Federal Constitutional Court (Bundesverfassungsgericht). According to Wikipedia (emphasis mine):
Specifically, it can vet the democratic and constitutional legitimacy of bills proposed by federal or state government, scrutinise decisions (such as those relating to taxation) by the administration, arbitrate disputes over the implementation of law between states and the federal government, and (most controversially) ban non-democratic political parties.
And from this blog about one particular law:
Once the law has passed the parliament’s upper house in a few weeks – a vote seen as all but assured – the bill will be presented to the German president Joachim Gauck for signature. If he believes the law is unconstitutional, he could either decline to sign it, or sign it, but at the same time ask the German constitutional court to verify its compliance with German Basic Law. Upon signature, the legislation will enter into effect, which then, of course, would still leave the law open to subsequent court challenges.
Acts of Dáil Éireann (the Irish Parliament) do not become law until signed by the president. The president can, if he wishes, first refer the Act to the Supreme Court to check that it does not conflict with the constitution. A few laws have been blocked that way.
This is not an automatic check that all laws pass through; it is an optional one, held at the discretion of the president.
The difficulty is that in many cases the courts have to balance the specific facts of a given case in order to test constitutionality. Absent such a case do we speculate on incredibly unlikely scenarios where a particular law may be deemed unfit? Or under what future circumstances it may be so deemed?
Oftentimes rather than a pure decision, instead legislatures may have a local legal group to look over a law for areas where they fell a judge MAY have issues with it.
Don't forget, in western jurisdictions the legal system is as much about the precedence of prior interpretation and/or application of a given law as much the written law itself.
And finally, judges / lawyers are not overly fond of giving opinions on how they might rule should a certain circumstance of a specific crime be brought before them as it implies a pre-prejudiced position on the law that may force them to recuse themselves from actually judging it for real. So if they say "yeah, I can see where someone could convince me that it is unconstitutional", they will not actually be able to sit on a real case of it as they have a pre-formed opinion. As such, it may hamper their advancement.