Judicial review is frequently described as courts overruling governments, which misdescribes what most courts are actually doing.
Lawfulness against merits
Courts in most systems assess whether a decision was made lawfully rather than whether it was a good decision.
Which means a decision can be lawful and unwise, and courts will generally not interfere with it.
The distinction is fundamental and is routinely blurred in coverage that describes rulings as courts disagreeing with policy.
The grounds
Vary between systems and generally cover a similar set.
Acting beyond the powers granted.
Procedural failure, including failure to consult where required or to give reasons.
Failure to consider relevant matters, or consideration of irrelevant ones.
Unreasonableness, at a threshold that is generally high.
And, in systems with them, violation of constitutional or human rights provisions.
Standing
Who may bring a challenge.
Which varies considerably — some systems require a direct personal interest, others permit public interest challenges.
Restrictive standing rules limit the decisions that can be challenged at all, which is a significant practical constraint.
Remedies
Courts typically quash a decision, requiring it to be made again lawfully.
Which frequently means the same decision can be reached through a proper process, and it is why successful challenges do not always change outcomes.
Declarations of incompatibility, in some systems, state that legislation conflicts with rights provisions without invalidating it, leaving the response to the legislature.
Constitutional review
Where courts can strike down legislation entirely.
Which exists in some systems and not others, and the difference is fundamental to how those systems work.
Systems without it rely on parliamentary sovereignty, with courts interpreting rather than invalidating legislation.
Appointment
Methods vary enormously, from executive appointment to judicial commissions to election.
Which affects perceived and actual independence, and the arrangements are frequently contested.
Where appointment is politically controlled, court composition becomes a political objective, which affects how rulings are perceived regardless of their reasoning.
Precedent
Common law systems treat previous decisions as binding, which produces predictability and constrains change.
Civil law systems place more weight on codes, with previous decisions carrying less formal weight.
Which affects how much a single ruling changes and how much argument focuses on distinguishing previous cases.
Judicial independence
Protected through tenure, salary protection and restrictions on removal in most systems.
Which exists because decisions frequently go against governments, and a judiciary that can be removed for that cannot perform the function.
International bodies monitor judicial independence, and erosion of it is a recognised warning indicator in comparative political research.
Reading a ruling
The reasoning matters more than the outcome, since it determines what the ruling applies to.
Judgments are published and are frequently more readable than expected, with summaries provided for significant cases.
Deference
How much weight courts give to the judgement of the body that made a decision.
Which varies by subject — courts generally defer more on technical, economic and security matters than on rights questions.
The standard of review determines outcomes substantially, and disputes about which standard applies are frequently the central issue in a case.
Interim relief
Courts can suspend a decision while a challenge proceeds.
Which matters enormously in practice, since litigation can take years and an unsuspended decision takes effect meanwhile.
Tests for interim relief generally weigh the strength of the case, the balance of harm and the public interest.
Cost
Litigation is expensive, and cost rules determine who can realistically bring a challenge.
Which is why cost-capping orders exist in some systems for public interest cases, and why legal aid availability affects what decisions are reviewable in practice.
The chilling effect of potential cost liability is a documented constraint on public interest litigation.
Ouster clauses
Legislative provisions attempting to exclude judicial review of particular decisions.
Which courts have generally interpreted narrowly, on the reasoning that excluding review of legality is constitutionally significant.
The tension between legislative supremacy and judicial oversight is most visible here, and it has produced landmark rulings in several systems.
Tribunals
Specialist bodies deciding disputes in particular fields, generally faster and less formal than courts.
Which handle enormous volumes of decisions affecting individuals — benefits, immigration, employment, tax.
Appeal rights from tribunals to courts vary, and restrictions on them have been a recurring policy question.
Following cases
Judgments are published, and courts increasingly publish accessible summaries for significant rulings.
Which is a considerably better source than coverage, since the reasoning determines what the ruling means for future cases.
Legal commentary from academic and practitioner sources is generally freely available and explains context that coverage omits.
Public law and private law
Judicial review concerns the exercise of public power, which distinguishes it from ordinary litigation between private parties.
Which means the boundary matters — bodies performing public functions can be subject to review even where they are not formally part of government.
Privatisation and outsourcing have complicated this, since services delivered by private companies under contract may fall outside review depending on how the tests are applied.