The Supreme Court has upheld a 2011 decision by the Court of Appeal that unemployed people were not given enough information, especially about the sanctions for refusing jobs under the schemes.
The judgement said that the two claimants "should have [been given] sufficient information about the scheme to be able to make freely informed representations".
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The town was where the US military and Kurdish fighters first united to defeat the Islamic State group four years ago.
MPs are expected to debate the deal on Saturday.
The duchess is expected to speak at the event, which will involve games, music and traditional Pakistani cakes.