Under Aid to Families With Dependent Children (AFDC), 49 Stat. 627, as amended, 42 U. S. C. § 601
et seq.,
the Federal Government partially reimburses States for welfare programs that either comply with all federal prescriptions or receive a waiver from the Secretary of Health and Human Services (HHS). 42 U. S. C. § 1315. California seeks to change its AFDC program by limiting new residents, for the first year they live in California, to the benefits paid in the State from which they came. See Cal. Welf. & Inst. Code Ann. §11450.03 (West Supp. 1994). Green and other new residents who receive AFDC benefits challenged the constitutionality of this California statute in a federal court action; they maintain that the payment differential between new and long-term residents burdens interstate migration and thus violates the right to travel recognized in
Shapiro
v.
*559
Thompson,
The California statute provides that the payment differential shall not take effect absent receipt by the State of an HHS waiver. See Cal. Welf. & Inst. Code Ann. § 11450.03(b) (West Supp. 1994). HHS originally granted a waiver, which was in effect when the District Court and Court of Appeals ruled. But “ripeness is peculiarly a question of timing,” and “it is the situation now rather than the situation at the time of the [decision, under review] that must govern.”
Regional Rail Reorganization Act Cases,
*560
In view of the impediment to dispositive adjudication, we direct the vacation of prior judgments in this case. As we explained earlier this Term, in deciding whether to disturb prior judgments in a case rendered nonjusticiable, we have inquired, pivotally, “whether the party seeking relief from the judgment below caused the [nonjusticiability] by voluntary action.”
U. S. Bancorp Mortgage Co.
v.
Bonner Mall Partnership, ante,
at 25. Unlike settlement, see
ibid.,
or a losing party’s decision to forgo appeal, see
Karcher
v.
May,
Accordingly, the judgment of the United States Court of Appeals is vacated, and the ease is remanded to that court with directions to order the vacation of the District Court’s judgment and the dismissal of the case.
It is so ordered.
