U.K. Home Secretary Theresa May introduced the immigration cap this summer as an interim measure while deciding the level of a permanent cap from April 2011, and it was quickly subject to legal challenges by groups claiming it was unfair to would-be immigrants, the BBC reported Friday.
The court found that ministers had "sidestepped" Parliamentary oversight and debate.
Britain's Prime Minister David Cameron has called for net migration to be lowered from its current level of almost 200,000 a year to "tens of thousands."
As a first move, ministers introduced a temporary cap for non-EU skilled workers of 24,100 a month in June, in line with a Conservative party election commitment.
The measure was challenged by the Joint Council for the Welfare of Immigrants and the English Community Care Association.
In Friday's ruling, the High Court said the home secretary had not gone through the proper parliamentary procedures before implementing the cap.
The Home Office has yet to respond to the ruling, the BBC said.