The Supreme Court has ruled that the benefit cap is "right and fair".
Not correct. The Supreme Court ruled that the benefit cap is legal, not that it's right or fair. The judgment can't be taken as an endorsement of this policy.
The benefit cap is lawful, ruled the Supreme Court by a majority of 3:2 last month. Iain Duncan Smith, Secretary of State for Work and Pensions, said that he was "delighted that the country's highest court has agreed with this government… that the benefit cap is right and fair".
This isn't an accurate representation of the Supreme Court's judgment, in which Lord Hughes noted that "reasonable people may well either agree or disagree" on the decision to cap benefits at £500 per week, "but to say that one disagrees is not the same as saying that the [cap] is unlawful".
The Court was careful to make clear that its role was to interpret the law, not to review the policy decision to set the cap at this level. As one judge put it, "it is in the political, rather than the legal arena, that the consequences of that must be played out".
A breach of a UN Convention, but not a breach of the law
Three of the five judges concluded that the benefit cap doesn't comply with the UN Convention on the Rights of the Child. Two of them, Lady Hale and Lord Kerr, were the minority who decided against the government as a result.
The third, Lord Carnwath, didn't agree that the Convention on the Rights of the Child carries enough weight in English law to affect the final ruling of the Court—so the government won. But he did express the hope that the government will review the cap, in the context of children's rights.
This shows that the judgment wasn't intended as an endorsement of the benefit cap.
Decision based on human rights law
The legally binding decision made by the Court was limited to whether the cap breached the European Convention on Human Rights (ECHR).
Specifically, the question was whether the cap discriminates against women, because of its impact on lone parents (who are overwhelmingly women).
This is a separate issue to whether it's 'right' from a values or policy perspective, or even by reference to the standards of international law.
One of the ways that the Court avoided making a value judgment in applying this test was by assessing whether the regulations introducing the cap were sufficiently thought through and reviewed; in Lord Reed's words, whether they had a "reasonable foundation".
In making this assessment, the majority pointed to factors such as the degree to which the cap had been reviewed by Parliament and the fact that the four Children's Commissioners had been actively involved in the wider debate on the cap.
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For more information on the way the benefit cap works read our briefing.