What is the scope of review of a motion for a preliminary injunction?

The initial question to be discussed is our scope of review when a district court denies a motion for a preliminary injunction. Ordinarily, such review is "limited to determining whether the trial court abused its discretion in finding the presence or absence of irreparable harm and a probability that the plaintiffs would succeed on the merits." Thornburgh v. American College of Obstetricians & Gynecologists, 476 U.S. 747, 106 S.Ct. 2169, 2176, 90 L.Ed.2d 779 (1986). But, an abuse of discretion standard is not an inflexible rule governing review when the district court's ruling is solely on the law and the facts are not of controlling relevance. When such is the case and with a full record before it, an appellate court need not accord the customary deference to the district court's discretion, but instead may employ its own plenary scope of review. Id. 106 S.Ct. at 2177. Because that is the precise circumstance of the instant appeal, that is to say, we have a complete factual record before us, and the question presented relates solely to a question of law, we undertake plenary review of the merits.

To succeed in their challenge, appellants must overcome accumulated judicial wisdom that the Secretary's view in this complex area is more expert than that of the courts. This proposition has been variously expressed as "an agency's construction of its own regulations is entitled to substantial deference." Lyng v. Payne, 476 U.S. 926, 106 S.Ct. 2333, 2341-42, 90 L.Ed.2d 921 (1986). Or, the mere existence of "more equitable" alternatives "does not render the Secretary's choice invalid." Knebel v. Hein, 429 U.S. 288, 294, 97 S.Ct. 549, 553, 50 L.Ed.2d 485 (1977) (upholding the Secretary's inclusion in income of a

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