Opinion of the Court
1
Problems begin with the very concept of an “undue burden.” As Justice Scalia noted in his Casey partial dissent, determining whether a burden is “due” or “undue” is “inherently standardless.” 505 U. S., at 992; see also June Medical Services L. L. C. v. Russo, 591 U. S. ___, ___ (2020) (Gorsuch, J., dissenting) (slip op., at 17) (“[W]hether a burden is deemed undue depends heavily on which factors the judge considers and how much weight he accords each of them” (internal quotation marks and alterations omitted)).
The Casey plurality tried to put meaning into the “undue burden” test by setting out three subsidiary rules, but these rules created their own problems. The first rule is that “a provision of law is invalid, if its purpose or effect is to place a substantial obstacle in the path of a woman seeking an abortion before the fetus attains viability.” 505 U. S., at 878 (emphasis added); see also id., at 877. But whether a particular obstacle qualifies as “substantial” is often open to reasonable debate. In the sense relevant here, “substantial” means “of ample or considerable amount, quantity, or size.” Random House Webster’s Unabridged Dictionary 1897 (2d ed. 2001). Huge burdens are plainly “substantial,” and trivial ones are not, but in between these extremes, there is a wide gray area.
This ambiguity is a problem, and the second rule, which applies at all stages of a pregnancy, muddies things further. It states that measures designed “to ensure that the woman’s choice is informed” are constitutional so long as they do not impose “an undue burden on the right.” Casey, 505 U. S., at 878. To the extent that this rule applies to pre-viability abortions, it overlaps with the first rule and appears to impose a different standard. Consider a law that imposes an insubstantial obstacle but serves little purpose. As applied to a pre-viability abortion, would such a regulation be constitutional on the ground that it does not impose a “substantial obstacle”? Or would it be unconstitutional on
