Only a week old, Illinois’ sweeping ban on high-powered firearms and large-capacity ammunition magazines is facing at least two legal challenges and pushback from dozens of county sheriffs who say they won’t uphold the law.

One lawsuit was filed Friday in state court in Crawford County, which borders Indiana in southern Illinois, on behalf of three residents who argue that the law violates their right to bear arms under the Second Amendment of the U.S. Constitution. Failed Republican attorney general candidate Thomas DeVore filed another lawsuit Tuesday in nearby Effingham County on behalf of four licensed firearm dealers and more than 850 other individuals who contend their rights are violated by the law.

Later Tuesday, the Illinois State Rifle Association issued a statement from its executive director saying the gun-rights group would be “filing a federal lawsuit imminently.”

The law took effect with Democratic Gov. J.B. Pritzker’s signature on Jan. 10. Pritzker and other supporters of the law anticipated legal challenges to the measure, passed in response to the deadly mass shooting at the Fourth of July parade in Highland Park, but have contended that the restrictions it places on firearm ownership are constitutional.

In addition to legal challenges, putting the law into practice has become an issue as sheriffs across the state, including in DuPage and other Chicago-area counties, have indicated they would not enforce the weapons ban on the grounds that it punishes law-abiding citizens by violating their Second Amendment rights.

DuPage Sheriff James Mendrick, a Republican, said in a news release Friday that he believed the law was “a clear violation” of the “inalienable right” to bear arms which his office would not participate in enforcing.

Mendrick was also criticized by newly elected DuPage County Board Chair Deb Conroy, a former Democratic state representative from Elmhurst, who said in a statement Friday, “In DuPage County, we should not be playing politics with state laws.”

On Tuesday, 16 Democratic state legislators who represent portions of the west suburban county said in an open letter to residents that they were “dismayed and angered” by Mendrick’s statement.

“The DuPage County sheriff’s intention to violate his sworn duty to uphold our state’s laws is a dereliction of duty and puts our safety at risk,” the lawmakers wrote. “The sheriff’s words send a clear message that lawbreakers are welcome here.”

Pritzker likewise has chided sheriffs who’ve come out against the law, saying enforcing its provisions is “their job.”

“And I expect them to do that job. … You can have all the resolutions and declarations that you want; the reality is that the laws that are on the books, you don’t get to choose which ones people are going to follow,” Pritzker said last week at an unrelated event in Quincy.

One gun control group called the sheriffs’ vow that they won’t enforce the law “disturbing” and said law enforcement agencies need to “come together” in understanding “how gun violence is devastating our communities.”

“This legislation was not a symbolic act — it’s a critical path to protect the lives of children and Black and brown communities in our state,” the group Gun Violence Prevention PAC, or GPAC, said in a statement. “Furthermore, the legislation serves as a safeguard for law enforcement as well.”

The Crawford County lawsuit names as defendants two people who are tasked with enforcing the law: Illinois State Police Director Brendan Kelly and Crawford County State’s Attorney Cole Price Shaner.

State Police spokeswoman Melaney Arnold declined to comment on pending litigation. Shaner could not be reached Tuesday for comment.

The lawsuit alleges that the law violates the Fourth and 14th amendments by requiring people who owned now-banned firearms at the time it took effect to “admit possession of certain firearms that under state law are generally declared to be unlawful.”

The complaint also alleges that the ban violates the Second Amendment, leaning heavily on a June decision from the U.S. Supreme Court that struck down New York state’s concealed carry law.

The Illinois law immediately bans the delivery, sale, import and purchase of guns that are designated in the law as “assault weapons.” Starting next year, people who possess guns covered by the ban must either register them with the state or face a misdemeanor for a first offense and a felony for subsequent offenses.

The law also immediately bans the delivery, sale or purchase of large capacity ammunition magazines of more than 10 rounds for long guns and 15 rounds for handguns. As of April 10, current owners’ possession of large-capacity magazines will be allowed only on private property, at a firing range or a sport shooting competition or at a federal licensed gun dealer for repairs. Violations will be subject to a $1,000 fine.

Also, devices that increase the firing rates of a firearm, known as “switches,” to turn them into semi-automatic or automatic weapons, are immediately banned and someone in possession would face a felony count for each device.

The new law also speeds up to July from January the existing requirement for universal background checks by federal firearm dealers or the Illinois State Police for private gun sales. It also modifies the state’s current “red flag” law that allows relatives and police to seek a court approved firearm restraining order to keep guns out of the hands of dangerous people, extending the duration of the orders from six months to a year.

Most Republicans contended the legislation would do nothing to prevent crime, would run counter to rulings by the U.S. Supreme Court involving Second Amendment rights and would face a court challenge upon becoming law.

In the Effingham County lawsuit, DeVore focuses largely on procedural issues under the state constitution, arguing that the process by which the measure was approved violated a requirement that legislation be confined to a single subject. In the final days of the their lame-duck session, lawmakers took a bill that was initially about insurance and overwrote it with the weapons ban.

While a common practice in Springfield, DeVore argues that “it’s an abhorrent method of excluding the public from participating in lawmaking so they might have a meaningful opportunity to make their voices heard to representatives.”

The lawsuit, which names Pritzker, House Speaker Emanuel “Chris” Welch, Senate President Don Harmon and Attorney General Kwame Raoul as defendants, alleges that lawmakers and the governor violated the state constitution’s due process and equal protection clauses.

Pritzker signed the bill just hours after House Democrats led final passage of the measure on a 68-41 vote, and a day after Senate Democrats approved it 34-20. Pritzker and legislators acted amid warnings from most Republicans and gun-rights advocates that the new law was unconstitutional and would face a legal challenge.

Two House Republicans — outgoing House GOP Leader Jim Durkin ofWestern Springs and Rep. Bradley Stephens of Rosemont — joined Democrats in voting for the bill. Four House Democrats voted against it. In the Senate, there were no GOP votes for the bill, while four Democrats voted against it.

dpetrella@chicagotribune.com

jgorner@chicagotribune.com