WASHINGTON – The Supreme Court on Monday effectively struck down Chicago’s strict firearms ban in a landmark decision that casts state and local gun laws into question.

The court ruled 5-4 that Chicago’s longstanding gun ban violated an individual’s right to own firearms, enshrined in the Second Amendment. The ruling marks the first time that the court has determined the Constitution restricts state and municipal gun-control powers.

“Self-defense is a basic right, recognized by many legal systems from ancient times to the present day,” Justice Samuel Alito wrote for the majority. “Individual self-defense is the central component of the Second Amendment right,” he said.

Alito was part of the court’s 5-4 majority that also struck down the gun ban in Washington, D.C., in 2008. The landmark District of Columbia v. Heller decision was the first time the court ruled that the Second Amendment’s right to bear arms extends to individuals, not just formal militias.

A lower court must still invalidate the Chicago law, a step the Supreme Court ruling makes all but certain.

Writing in dissent Monday, Justice Stephen Breyer – joined by justices John Paul Stevens, Ruth Bader Ginsburg and Sonia Sotomayor – noted that handguns cause an estimated 60,000 deaths and injuries each year. Breyer cautioned that the ruling will hinder state and local efforts to control the carnage.

“Unlike other forms of substantive liberty, the carrying of arms for that purpose often puts others’ lives at risk,” Breyer warned.

Alito’s 45-page majority opinion, issued on the last day of the Supreme Court’s 2009-10 term, built directly on the earlier Washington decision and emphasized throughout the traditional deference that courts and legislatures have paid to gun ownership. Alito was joined in the majority by Chief Justice John Roberts Jr. and justices Antonin Scalia, Anthony Kennedy and Clarence Thomas.

“King George III’s attempt to disarm the colonists in the 1760s and 1770s provoked polemical reactions by Americans invoking their rights as Englishmen to keep arms,” Alito said.

Alito noted that for the authors of the Bill of Rights, which includes the Second Amendment, “the right to keep and bear arms was considered no less fundamental.”

Alito, as Scalia did in the Washington gun case, noted that “the right is not unlimited,” but Monday’s decision shed little light on what kinds of state and local gun laws might survive the next round of legal challenges. In general, though, the stricter the law, the easier it may be to challenge.

“Regulatory measures such as prohibiting the possession of firearms by felons and the mentally ill, and laws that prohibit possession of guns in sensitive locations such as schools do not run afoul of the Second Amendment,” suggested Steven Puiszis, a Chicago-based lawyer with the firm Hinshaw & Culbertson.

Democratic Sen. Patrick Leahy of Vermont, the chairman of the Senate Judiciary Committee, said “states and local governments will now have to proceed more carefully when enacting gun regulations.”

The Second Amendment says that “a well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed.”

The first 10 constitutional amendments that make up the Bill of Rights cover only the federal government. The 14th Amendment, added after the Civil War, also declares that “no state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States.” Over time, the Supreme Court has determined that most of the Bill of Rights’ provisions apply to the states as well as the federal government as a result of the 14th Amendment.

“It is clear that the framers and ratifiers of the 14th Amendment counted the right to keep and bear arms among those fundamental rights necessary to our system of ordered liberty,” Alito wrote.

The challenge in the case, called McDonald v. City of Chicago, culminated a years-long litigation campaign by gun rights groups, which have used carefully selected sympathetic plaintiffs to dispute the nation’s strictest laws. The lead plaintiff for the Chicago case was Otis McDonald, a community activist in his late 70s who lives in a high-crime neighborhood.

Chicago’s ordinance, like Washington’s, effectively bans the possession of handguns by most city residents. It bars firearms possession unless an individual holds a valid license, and those licenses haven’t been issued in many years.