The Supreme Court divided along ideological lines Tuesday in ruling that states may not be sued by their employees for illegally denying them medical leave.

States are generally immune from lawsuits seeking monetary damages, and the court’s conservative majority said in a 5 to 4 decision that the restriction should apply when the issue at stake is the sick-leave provisions in the federal Family and Medical Leave Act.

The court ruled differently on another portion of the law in 2003. It said that violating its family-leave provisions could open a state to lawsuits.

Justice Anthony M. Kennedy, who wrote Tuesday’s decision, said that is because Congress had found evidence that states “had family-leave policies that differentiated on the basis of sex and that states administered even neutral family-leave policies in ways that discriminated on the basis of sex.”

But Kennedy said Congress had not found evidence of discrimination or sex stereotyping when it came to sick leave. Without that, the majority said, the usual protections against suing a state should not be lifted.

The U.S. Supreme Court Building in Washington. (J. Scott Applewhite/AP)

The court’s liberal members disagreed with the ruling, and Justice Ruth Bader Ginsburg summarized their dissent from the bench, an act normally reserved for disagreements of special consequence.

Ginsburg said the majority missed the point that the act in its entirety shields women from discrimination.

“The best way to protect women against losing their jobs because of pregnancy or childbirth, Congress determined, was not to order leaves for women only, for that would deter employers from hiring them,” said Ginsburg, who was joined by Justices Stephen G. Breyer, Sonia Sotomayor and Elena Kagan.

“Instead, Congress adopted leave polices from which all could benefit.”

Ginsburg, who had a reputation as a women’s rights advocate before she joined the court, pointed out that Tuesday’s decision affects only government employers and that the act still “applies, undiluted, in the private sector.”

The case was brought by Daniel Coleman, who tried to sue his employer, the Maryland state Court of Appeals. He had asked for a 10-day medical leave in 2007 to deal with hypertension and diabetes and was fired after his request was denied.

The FMLA allows employees to take up to 12 weeks of unpaid leave per year for the birth, care or adoption of a child; the care of a family member with a serious health problem; or the employee’s serious health condition that interferes with the ability to work.

In a 2003 case, Nevada Department of Human Resources v. Hibbs,the court upheld a lawsuit against a state employer for violating the family-care provisions of the act, citing Congress’s finding of sex-based discrimination in family leave policies.

But Kennedy said that there was no evidence that when Congress passed the legislation it found similar discrimination in granting sick leave, and that therefore the usual bar on state immunity “as sovereigns in our federal system” should remain in place.

Chief Justice John G. Roberts Jr. and Justices Clarence Thomas and Samuel A. Alito Jr. joined Kennedy’s opinion, while Justice Antonin Scalia agreed with the outcome.

The case is Coleman v. Court of Appeals of Maryland .