WASHINGTON (Reuters) - The U.S. Supreme Court steered clear on Tuesday of another major dispute over gun rights, turning away appeals of a judicial ruling backing a Democratic-backed ban in Illinois on assault-style rifles such as AR-15s.

The justices declined to hear a group of cases appealing a lower court's rejection of the challengers' argument that the ban violates the right to keep and bear arms under U.S. Constitution's Second Amendment.

The legal dispute centers on whether assault rifles are weapons that are chiefly useful in military service and thus may be subject to a ban. The Supreme Court, in a landmark 2008 ruling expanding gun rights, noted that "M-16 rifles and the like" are not protected under the Second Amendment.

The availability of assault rifles, which are popular among gun enthusiasts, continues to fuel fierce debate in a nation bitterly divided over how to address firearms violence including frequent mass shootings.

The Supreme Court, which has a 6-3 conservative majority, has taken an expansive view of Second Amendment rights.

In 2022, the court recognized a constitutional right to carry a handgun in public for self defense in a decision that struck down New York state gun limits on carrying concealed firearms.

That ruling established a legal standard that could make it harder for lower courts to sustain new or existing gun regulations, requiring such measures to be comparable with the nation's "historical tradition" of firearm restrictions.

However, the court clarified on June 21 that modern restrictions need a historical "analogue" but not a "twin" in a ruling that upheld a federal gun possession ban targeting domestic abusers, signaling the limits of the Bruen standard.

A federal assault weapon ban enacted in 1994 lapsed a decade later and has not been renewed by Congress despite Democratic efforts. In the absence of broad action by Congress on gun control, some states have enacted various measures, often drawing legal challenges on Second Amendment grounds.

The Illinois law bans the sale and distribution of many kinds of high-powered semiautomatic "assault weapons," including AK-47 and AR-15 rifles, as well as magazines that take more than 10 rounds for long guns and 15 rounds for handguns. The ban was passed in 2023 after a massacre at a 2022 Independence Day parade in the Chicago suburb of Highland Park that killed seven people.

Several groups of plaintiffs contested the state's ban on assault weapons and large-capacity magazines in federal and state courts.

The Chicago-based 7th U.S. Circuit Court of Appeals ruled in November 2023 that the challengers were unlikely to succeed in their challenges, in part because the Second Amendment does not apply to the banned rifles and magazines, which it concluded "are much more like machine guns and military-grade weaponry than they are like the many different types of firearms that are used for individual self-defense."

The Supreme Court previously rebuffed efforts by certain of the plaintiffs to block the Illinois law as the litigation played out.

In court papers, Illinois said that 14 states have enacted laws restricting certain types of semiautomatic firearms or magazines that allow shooters to fire rapidly without reloading "making them the instruments of choice in mass shootings."

The Supreme Court on May 20 declined to hear a challenge to a Democratic-backed ban in Maryland on assault-style rifles while that litigation continues in a lower court.

The justices also acted on another important gun-related case this year, rejecting on June 14 a federal ban on "bump stock" devices that enable semiautomatic weapons to fire rapidly like machine guns.

(Reporting by Andrew Chung; Editing by Will Dunham)

By Andrew Chung