Setback for migrant worker rule
The Home Office has suffered a potentially serious legal setback in its efforts to reduce the numbers of migrant workers in the UK.
The Supreme Court said ministers could not bar workers unless rules used to do so had been shown to Parliament.
The Home Office said it would act quickly to ensure the judgement requirements were met.
Home Affairs Committee chairman Keith Vaz said the ruling had delivered a "hammer blow" to the current system.
The judgement could have implications for many rejected cases since 2008 - or possibly earlier.
Supreme Court deputy president Lord Hope said Parliament must see rules before they could be used.
And fellow judge Lord Dyson warned Parliament's system for overseeing immigration rules may no longer be fit for purpose, given the workload it could now face.
The ruling came in the case of Hussain Zulfiquar Alvi, a Pakistani man who came to the UK in 2003 as a student. He stayed on after his studies to become a physiotherapy assistant.
In 2009, he applied for further leave to remain under revised rules for migrant workers called the Points-Based System. The system, which came into force in 2008, uses points to calculate which migrants have the most skills and would be of most benefit to the UK.
The Home Office said Mr Alvi could not stay because he did not have enough skills to earn sufficient points.
But Mr Alvi said the decision was unlawful because Parliament had not actually been shown the specific Home Office-set rules relating to his occupation.
Under a 40-year-old law, Parliament's Scrutiny Committee must examine all changes to immigration rules.
In its judgement, the Supreme Court said the occupation list which applied to the decision in Mr Alvi's case was clearly part of the immigration rules that needed to be examined by Parliament, because MPs and peers wanted a say in how immigration was being controlled.
Lord Hope, the lead justice in the case, said he recognised the judgement could create a huge workload for Parliamentarians.
He said: "The situation that has created this problem is so far removed from what it was in 1971 that one wonders whether the system that was designed over 40 years ago is still fit for its purpose today."
The full implications of the ruling are not yet clear, but legal sources have told the BBC that it could be one of the most important judgements on immigration in a decade.
Lord Dyson, agreeing with Lord Hope's leading judgement, criticised the modern immigration system.
"It is... a striking fact that the immigration rules are already hugely cumbersome," he said.
"The complexity of the machinery for immigration control has (rightly) been the subject of frequent criticism and is in urgent need of attention."
A Home Office spokesperson said: "We will act quickly to ensure the requirements of this judgment are met and that the necessary guidance is transferred into the Immigration Rules.
"Today's judgment supports our ongoing work to simplify the immigration system and minimise legal challenge in future."
The rules in the Alvi case are expected to be laid before Parliament before the end of the week, complying with the judgement.
Shahram Taghavi, deputy head of immigration at Lewis Silkin LLP law firm, said: "Today's ruling will have a profound impact upon the current corporate immigration system, and effectively represents a wholesale collapse of the legal framework for immigration policy in the UK.
"This decision will no doubt reverberate loudly and widely, given the sheer number of cases on related matters winding their way through the Courts at present. Had the Home Office and Secretary of State elected to pursue changes to immigration in the proper way - through Parliamentary review and scrutiny - it is clear that this chaotic situation could have been avoided."
Mr Vaz said: "This judgement delivers a hammer blow to the Points-Based System. The court is very clear that ministers must place rules before Parliament for proper scrutiny.
"Their failure to do so over a number of years leaves the immigration system open to ridicule. Thousands of people will not know whether or not they are allowed to stay in the country."
He added: "I have written to the Home Secretary to ask what steps she intends to take to deal with this judgement.
The Migration Observatory think-tank at Oxford University said it was a "potentially very significant development" that could call into question the validity of immigration rules as a whole.
"This could open the government up to an enormous number of legal challenges, not only from labour migrants, but also from family migrants and others," a spokesperson said.