"To implement its holding, Casey rejected both Roe’s rigid trimester framework and the interpretation of Roe that considered all previability regulations of abortion unwarranted. 505 U. S., at 875–876, 878 (plurality opinion). On this point Casey overruled the holdings in two cases because they undervalued the State’s interest in potential life. See id., at 881–883 (joint opinion) (overruling Thornburgh v. American College of Obstetricians and Gynecologists, 476 U. S. 747 (1986) and Akron v. Akron Center for Reproductive Health, Inc., 462 U. S. 416 (1983)). We assume the following principles for the purposes of this opinion. Before viability, a State “may not prohibit any woman from making the ultimate decision to terminate her pregnancy.” 505 U. S., at 879 (plurality opinion). It also may not impose upon this right an undue burden, which exists if a regulation’s “purpose or effect is to place a substantial obstacle in the path of a woman seeking an abortion before the fetus attains viability.” Id., at 878. On the other hand, “[r]egulations which do no more than create a structural mechanism by which the State, or the parent or guardian of a minor, may express profound respect for the life of the unborn are permitted, if they are not a substantial obstacle to the woman’s exercise of the right to choose.” Id., at 877. Casey, in short, struck a balance. The balance was central to its holding. We now apply its standard to the cases at bar."