“Under Section 1334, [Office of Personnel Management]-sponsored plans would compete nationwide against private health insurance. In effect, Congress is creating a special set of plans, governed by special rules, in a closed national ‘market.’ Instead of fair competition with private health plans, Congress is sponsoring the equivalent of a national monopoly. That the OPM-sponsored plans are offered by private contractors (like Medicare contractors) is irrelevant. For consumers, it is hard to imagine anything worse than a government-sponsored ‘private’ monopoly.”