  This view traces the intelligibility of fundamental challenges about the grounds of law to unusual moral views about the legal relevance of some factor. If this is correct, we should expect that such challenges may occur with some regularity, and that arguments once widely considered not colorable may come to be taken seriously and finally to become dominant. The quick transition, from nonstarter to endorsement by the US Supreme Court, of the view that the Constitution limits legislative authority to regulate private civilian uses of firearms (District of Columbia v. Heller, 554 US 570 (2008) (07–290)), or of the view that the regulatory powers of the federal government do not extend to mandating the purchase of health insurance (National Federation of Independent Business v.  Sebelius, cited above), are recent illustrations.