After Soeharto stepped down in 1998, Indonesia began a radical decentralization program, one aspect of which was granting wide-ranging lawmaking powers to subnational governments. The national legislation establishing the decentralization framework gave power to the central government to review provincial-level laws, and, from 2014, for provincial governors to review city and county laws, and to invalidate them if they are inconsistent with national laws, morality, or public order. In 2017, the Constitutional Court declared these review mechanisms unconstitutional, deciding that these reviews should be conducted by the Supreme Court rather than the national or provincial executive governments. This decision reversed the trend of successive reforms from 2004 that had begun restoring political and legal power to the centre. It was also one of the most problematic in the Court’s history, as this article demonstrates. The legal reasoning was poor and incomplete, the Court appeared to be equally split (though the Court did not acknowledge this), and the consequences of the decision (which the Court did not appear to consider) are likely dire. The decision has caused great confusion, but despite its flaws may well lead to reforms requiring the Constitutional Court, rather than the Supreme Court, to review subnational laws.