Story Highlights • 5-4 ruling could open door to revisiting Roe v. Wade

• Justice Kennedy: Law does not violate constitutional right to abortion

• New justices Alito, Roberts provided solid conservative majority to uphold ban

• Federal law has never gone into effect pending court rulings

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WASHINGTON (CNN) -- The Supreme Court on Wednesday upheld a law that banned a type of late-term abortion, a ruling that could portend enormous social, legal and political implications for the divisive issue.

The sharply divided 5-4 ruling could prove historic. It sends a possible signal of the court's willingness, under Chief Justice John Roberts, to someday revisit the basic right to abortion guaranteed in the 1973 Roe v. Wade case.

President Bush, who signed the law in 2003 and appointed two of the justices who upheld it, said the prohibition "represents a commitment to building a culture of life in America."

"Today's decision affirms that the Constitution does not stand in the way of the people's representatives enacting laws reflecting the compassion and humanity of America," he said in a statement released by the White House.

At issue is the constitutionality of a federal law banning a rarely performed type of abortion carried out in the middle-to-late second trimester. (Watch how the decision might affect Roe vs. Wade )

The legal sticking point was that the law lacked a "health exception" for a woman who might suffer serious medical complications, something the justices have said in the past is necessary when considering abortion restrictions.

In the majority opinion, Justice Anthony Kennedy, the key swing vote in these divided appeals, said the federal law "does not have the effect of imposing an unconstitutional burden on the abortion right." He was joined by his fellow conservatives, Justices Antonin Scalia, Clarence Thomas, Samuel Alito and Roberts.

Sole woman on bench reads bitter dissent

In a bitter dissent read from the bench, Justice Ruth Bader Ginsburg, the only woman on the high court, said the majority's opinion "cannot be understood as anything other than an effort to chip away a right declared again and again by this court, and with increasing comprehension of its centrality to women's lives."

She called the ruling "alarming" and noted the conservative majority "tolerates, indeed applauds, federal intervention to ban nationwide a procedure found necessary and proper in certain cases" by doctor's groups, including gyncecologists.

The Justice Department and abortion rights groups have offered differing views of the legislation's impact on women's overall second trimester access to the procedure, and whether the procedure is ever medically necessary.

This was the first time the high court had heard a major abortion case in six years, and since then, its makeup has changed, with Roberts and Alito now on board.

Their presence on the bench provided the solid conservative majority needed to allow the federal ban to go into effect, with Kennedy providing the key fifth vote for a majority.

Alito replaced Sandra Day O'Connor, a key abortion rights supporter over her quarter century on the bench.

"A lot of us wish that Alito weren't there and O'Connor were there," Senate Majority Leader Harry Reid, D-Nevada, who opposed Alito's nomination, said.

Doctors call this type of late-term abortion an "intact dilation and evacuation." Abortion foes term it a "partial-birth abortion."

Three federal appeals courts had ruled against the government, saying the federal Partial-Birth Abortion Ban Act of 2003 is unconstitutional because it does not provide a "health exception" for pregnant women facing a medical emergency. The outcome of this latest challenge before the court's new ideological makeup could turn on the legal weight given past rulings on the health exception.

In states where such exceptions are allowed, the lists of possible health risks include severe blood loss, damage to vital organs and loss of fertility. Court briefs noted pregnant women having the procedure most often have their health threatened by cancer, heart disease, high blood pressure or risk of stroke. Doctors are given the discretion to recommend when the late-term procedure should be performed.

The federal law has never gone into effect, pending the outcome of nearly three years of legal appeals.

Specifically, the ban encompasses what doctors call "intact dilation and evacuation" (also known as IDX), which Congress in its legislation termed inhumane.

It is a rarely used second-trimester procedure, designed to reduce complications to the woman. More common is "dilation and evacuation" (D&E), used in 95 percent of pre-viability second-trimester abortions, according to Planned Parenthood. Both are generally performed after the 21st week of pregnancy.

A major part of the legal dispute was whether the federal ban also includes the relatively more common "standard D&E abortions." The government contends the law does not, and is sufficiently narrow not to place an "undue burden" on a woman's reproductive choices.

Raw numbers were also at the heart of the debate, because the two sides disagreed on how often the procedure is performed. Solicitor General Paul Clement, the Justice Department's top lawyer before the court, suggested it is rarely performed, and that other medical options are available, so banning it would therefore not be a real barrier to women.

Abortions rights supporters say "intact" abortions are a medically accepted pre-viability, second-trimester procedure.

Since the Roe v. Wade decision legalizing abortion, some states have tried to place restrictions and exceptions on access to the procedure, prompting a string of high court "clarifications" on the issue over the years.