On December 15, 2023, the U.S. Court of Appeals for the Fifth Circuit issued its decision in Illumina, Inc. v. FTC. Although the court vacated and remanded the Commission’s order to divest Grail based on the Commission’s treatment of the merging parties’ rebuttal evidence, it largely upheld the Commission’s decision. On December 17, 2023, after losing at the Fifth Circuit and following an EU order to unwind the merger, Illumina announced that it would divest Grail. Although notable for its application of substantive vertical merger law, the Fifth Circuit also grappled with what has become an increasingly common feature of administrative law: challenges to the constitutionality of administrative proceedings. After the Supreme Court’s decision in Axon Enterprise, Inc. v. FTC to allow constitutional challenges to be brought in district court without first exhausting agency review procedures, such challenges are becoming more common.