"In Casey, the Supreme Court issued an elaborately splintered decision in which the joint opinion, written by Justice O'Connor and joined by Justices Kennedy and Souter, announced the judgment and opinion of the Court. The Casey joint opinion effected three principal changes to Supreme Court abortion jurisprudence: it reaffirmed "the essential holding of Roe v. Wade,"' struck down the Roe trimester framework, and replaced it with a new undue burden standard."