The Supreme Court considered the best interests principle in the immigration, asylum and nationality context twice during 2013. Both cases continued the trend of the contraction of the principle in the higher appellate courts.
In Zoumbas v SSHD  UKSC 74, the Court considered a Scottish case in which the appellant and his wife, nationals of the Republic of Congo, were described as having ‘an unedifying immigration history’ (). They had met and married in the UK and went on to have three children together. In 2010, the appellant made further submissions under Article 8. The Secretary of State refused to consider the further submissions to be a fresh claim and the appellant’s claim for judicial review of this decision was dismissed at each level of the Scottish appellate pyramid. The Supreme Court also dismissed the appeal. Lord Hodge delivered the judgment of the Court. The (apparently undisputed) legal principles in this area are set out at  of the judgment and are worth giving careful consideration.
Two aspects of the judgment are particularly noteworthy. First, counsel for the appellant had sought to rely upon the dictum of Lord Kerr in ZH (Tanzania) v SSHD  UKSC 4 at  that ‘What is determined to be in a child’s best interests should customarily dictate the outcome of cases such as the present, therefore, and it will require considerations of substantial moment to permit a different result’.
In response, Lord Hodge held ():
In our view, it is important to note that Lord Kerr JSC’s formulation spoke of dictating the outcome of cases “such as the present” and that in the ZH (Tanzania) case the court was dealing with children who were British citizens. […] Moreover in the H (H) case  1 AC 338, para 145, Lord Kerr JSC explained that what he was seeking to say was that no factor should be given greater weight than the interests of a child.
This appears to have been a fairly dubious interpretation of what Lord Kerr had said at  of H (H) v Deputy Prosecutor of the Italian Republic  UKSC 25: in that paragraph he was, in fact, addressing what he had meant by ‘a primacy of importance’ in ZH (Tanzania) at . The significance of this is that Lord Kerr has never formally resiled from the proposition that the child’s best interests should customarily dictate the outcome of cases and that it will require considerations of substantial moment to permit a different result. There is, however, a significant caveat to this: Lord Kerr was on the panel in Zoumbas and did not deliver a judgment of his own objecting to Lord Hodge’s interpretation of what he had said in H (H).
Secondly, the Court found that the decision-maker’s assumption that the appellant and his wife would be removed to the Republic of Congo when assessing the best interests of their children did not render that assessment flawed (). This troubling conclusion represents a significant further dilution of the requirement, per Baroness Hale at  of ZH (Tanzania), for the best interests of the child to be ‘considered first’.
In R (AA (Afghanistan)) v SSHD  UKSC 49, the Court considered a case in which a child had been detained in the mistaken but reasonably held belief that he was an adult. The Court accepted that a ‘material breach’ of section 55 Borders, Citizenship and Immigration Act 2009 would render detention unlawful () but went on to find that there would not be a material breach where the Secretary of State’s published policies had been properly applied (). On the facts of the case, there had been no material breach.
Practitioners should note that the Court explicitly disapproved of AMM (A Child) v SSHD  EWHC 2567 (QB) in so far as Lang J’s judgment in that case amounted to her holding that any detention of a child in the mistaken but reasonable belief that he or she was aged over 18 years would, ipso facto, amount to a breach of section 55 ().