In his ruling, Lord Justice Pill said the Poundland work scheme case raised a question of "statutory construction".
He said the challenge was to the lawfulness of the 2011 Government regulations made by Ian Duncan Smith, Secretary of State for Work and Pensions, under sections of the Jobseekers Act 1995.
The judge said he was "unable to conclude that the statutory requirement for the regulations to make provision" for back-to-work schemes "of a prescribed description" had been met.
He ruled: "The statutory requirement is that the prescribed description is in the regulation."
Declaring the regulations unlawful, the judge said they must be quashed since their central purpose was to impose "requirements" on jobseeker allowance claimants and sanctions for failing to comply.
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