The Groton-based Connecticut Citizens Defense League and other gun-rights groups put the state on notice Friday that they plan to appeal a federal judge’s ruling upholding the constitutionality of the gun law passed in the wake of the Sandy Hook school shooting.

“Ding! Ding! Ding! Round Two Begins,” read the headline on a CCDL blog post announcing that the lead attorney for the plaintiffs in Shew v. Malloy had filed a notice of intent to appeal the decision issued Thursday by U.S. District Judge Alfred V. Covello.

A coalition of individuals and nonprofit groups, including CCDL and the Coalition of Connecticut Sportsmen, is challenging Public Act 13-3, passed in April 2013 in response to the murder of 20 children and six adults at a Newtown elementary school by a heavily armed Adam Lanza.

The new law added to the state’s existing list of banned assault weapons, bringing the total to 183, limited the capacity of ammunition magazines to l0 rounds or less, required background checks for all weapon sales and established a statewide registry for people convicted of crimes involving dangerous weapons.

The legal battle is moving to the Second Circuit Court of Appeals, a panel that Brian T. Stapleton, lead attorney for the plaintiffs, admitted “takes a very restrictive view of Second Amendment rights.” He said during a phone interview Friday that gun control advocates think the Second Circuit Court’s positions are reasonable, while people against gun control find them hostile. “We have always said this case is going to be fought and won on appeal,” Stapleton said. “Will we get the relief we are seeking in the Second Circuit? I don’t know and I’m not going to predict. If we don’t, we will try to take it to the Supreme Court.”

One of the court’s most recent gun control rulings, Kachalsky v. Cacace in 2012, upheld New York’s strict law on gun permits and carrying concealed pistols outside the home.

Scott Wilson of New London, president of the CCDL, said the group has grown from 2,499 members to nearly 12,000 since the Sandy Hook shooting. He said the group has been able to help fund the lawsuit through fundraisers and sweat equity.

While disappointed with Thursday’s decision, Wilson said it was not unexpected. “Ultimately, we believe in the judicial process and we have to let it play out,” he said.

In the 47-page ruling, Covello wrote that while Public Act 13-3 “burdens the plaintiffs’ Second Amendment rights, it is substantially related to the important governmental interest of public safety and crime control.” Covello wrote that the legislation was not written “with the utmost clarity” but is not unconstitutionally vague.

Gov. Dannel P. Malloy issued a statement praising Covello’s ruling, and state Attorney General George Jepsen vowed to vigorously defend the strict new gun laws in court.

Mark Barden, whose 7-year-old son, Daniel, was murdered by Lanza, released a statement Friday on behalf of Sandy Hook Promise, the nonprofit group he founded in response to the school shooting. “We have been following this case closely and have read the legal documents that were submitted,” Barden said. “We believe Judge Covello was correct in upholding the Connecticut law, which protects both the Second Amendment rights of our citizens and protects our children from gun violence.”

k.florin@theday.com