Judicial Review

Judicial review is the process by which the courts review actions of the other arms of government

Generally speaking, the law that applies for Judicial Review applies UK wide (City of Edinburgh v Secretary of State for Scotland) although of course there are minor proceedural variations, and the Scotland Act 1998 only applies within Scotland.

Illegality
This is also known as Ultra Vires - a an action taken beyond the authority given by statute, and compatibl eiwth basic common law/consitutional rights.

An example of this in play is HM Treasury vs Ahmed ; Ahmed was suspected of having links with terrorism. A UN Security Council resolution required all states to freeze bank accounts. The United Nations Act 1946 allows the government (via Order in Council) to put into effect Security Resolutions. Ahmed argued this was Ultra Vires - the original act was meant to apply to resolutions for states, and the idea that resolutions would apply to people was beyond the comprehension of parliament at the time.

This was struck down as Ultra Vires as the legislation was not intended to be targeted at people, and the court will generally require greater justification when basic rights are at stake - especially when there was no redress.