Opinion of the Court
II
We first address Transform’s mootness claim. A “case becomes moot only when it is impossible for a court to grant any effectual relief whatever to the prevailing party.” Chafin v. Chafin, 568 U. S. 165, 172 (2013) (internal quotation marks omitted). The case remains live “ ‘[a]s long as the parties have a concrete interest, however small, in the outcome of the litigation.’ ” Ibid.
Stripped of its baubles, Transform’s mootness argument is that MOAC’s ultimate relief hinges on the Bankruptcy Court’s ability to “reconstitut[e the leasehold] as property of the estate.” Brief for Respondent 19. Transform asserts that such reconstitution is impossible unless the leasehold transfer is “avoid[ed]” under 11 U. S. C. §549, which permits a debtor in possession to void certain transfers of estate property made after the bankruptcy case commences. But, according to Transform, only Sears can use §549. And, per Transform, not only did Sears waive any such avoidance claims in the Sale Order, but the time for using §549 has now expired. The upshot for Transform’s mootness argument is that no legal vehicle remains available for undoing the lease transfer, and therefore MOAC cannot possibly obtain any effectual relief, irrespective of our answer to the question presented.
Our cases disfavor these kinds of mootness arguments. In Chafin, for example, a mother invoking the Hague Convention on the Civil Aspects of International Child Abduction sought, and received, an order from a Federal District Court that her child be returned to Scotland from the United States, where the child was residing with her father. 568 U. S., at 168–171. The father appealed, seeking reversal and a concomitant “ ‘re-return’ ” order, id., at 171, 173, but in the interim the mother had removed the child to Scotland, so the appellate court dismissed the father’s appeal as moot. Id., at 171. Before us, the mother defended the moot-
