In its 2000 decision Stenberg v. Carhart, the Supreme Court struck down a Nebraska law prohibiting "partial birth" abortions -- where the baby would be partially out of the uterus, then the doctor would cut or crush the skull to complete the abortion. It is a disgusting procedure. The Court was split 5-4 with O'Connor, Breyer, Souter, Ginsburg and Stevens in the majority. Anthony Kennedy signed onto the (in)famous Planned Parenthood v. Casey decision in 1991 that reiterated the principle underlying Roe v. Wade and sought to establish a framework for determining what, if any, restrictions on the right to abortion could be valid. In 2000, Kennedy went ballistic -- he said the Court's ruling violated the principle in Casey that states could seek to preserve pre-natal life in a manner not inconsistent with the right to abortion.
Today, Kennedy and a 5-4 majority upheld the Federal Partial Birth Abortion Act that Pres. Bush signed in 2003. It is the first Supreme Court victory for abortion opponents. Congress enacted the FPBA in response to Stenberg and explicitly found that the partial-birth procedure was NEVER necessary for the health of the mother. The 5-4 majority, applying the Casey framework and allowing challenges to the ban if the mother's health is at issue, rejected a facial attack on the act. A "facial challenge" to an enactment asserts that there is no circumstance in which the statute can be constitutional. Thus, the Court's ruling means that the act is valid unless a claimant can prove otherwise based on her personal situation (an "as applied challenge").
The difference in this case from Stenberg: Samuel Alito. He's O'Connor's replacement and joined Kennedy's majority opinion. If this decision does not get the Evangelical Right prepared to fight for the Republican nominee in 2008, that group should forego any political actions.