The Supreme Court said Tuesday it was declining, for now, to hear challenges against an Illinois ban on assault weapons — cases that have quickly turned into a major test of the legality of the popular AR-15 rifle.

Justice Clarence Thomas indicated that his colleagues thought the cases weren’t yet ripe for the high court and needed more development before lower judges.

But he said the issue will have to be dealt with as the justices continue to figure out the extent of the Second Amendment and to what, whom, where and when it applies.

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“We have never squarely addressed what types of weapons are ‘Arms’ protected by the Second Amendment,” Justice Thomas wrote in a statement about the refusal.

Justice Samuel A. Alito Jr. said he would have taken the cases right now.

Justice Thomas said it’s particularly important that the justices decide whether AR-15-style rifles are protected.

The 7th U.S. Circuit Court of Appeals, which has allowed Illinois’ ban to go into effect while the challenges are being argued, has ruled that AR-15s are “militaristic” and so are beyond protection of the Second Amendment.

Judge Diane Wood said she sees the AR-15, a semiautomatic weapon, as nearly equivalent to automatic rifles carried by the U.S. military.

“Indeed, the AR-15 is almost the same gun as the M16 machinegun. The only meaningful distinction, as we already have noted, is that the AR-15 has only semiautomatic capability (unless the user takes advantage of some simple modifications that essentially make it fully automatic), while the M16 operates both ways,” Judge Wood wrote.

Justice Thomas called her ruling “contrived” and “contorting.”

“It is difficult to see how the Seventh Circuit could have concluded that the most widely owned semiautomatic rifles are not ‘Arms’ protected by the Second Amendment,” he wrote.

Illinois says its law is aimed not at particular weapons but rather at features it says make them bad for “civilian self-defense” but good for “offensive combat-specific uses.”

That includes rifles with detachable magazines coupled with another feature, such as a pistol grip, a flash suppressor, a barrel shroud or a telescoping stock.

It also includes rifles with fixed magazines that hold more than 10 rounds of ammunition at a time.

The state bars future purchases but lets those who already own a prohibited firearm keep them, as long as they are registered with the state.

Justice Thomas said that law is now on a collision course with the high court, which has been blazing new ground in interpreting the Second Amendment over the last 20 years.

It started with the 2008 Heller decision that established the right to bear arms for individuals and culminated in the Bruen ruling two years ago that said gun restrictions established a history-based test.

The Supreme Court issued a ruling last month deciding that some citizens can be prohibited, at least temporarily, from owning weapons under the Second Amendment.

But that still leaves myriad cases making their way through lower courts concerning restrictions on the frequency of sales, places where weapons can be banned, and  — as with the Illinois law — the types of weapons that can be regulated.