FILE PHOTO: A man stands outside the U.S. Supreme Court in Washington, U.S., June 27, 2019. REUTERS/Carlos Barria/

WASHINGTON (Reuters) - The daughter of a woman killed in a 2012 mass shooting will not be able to sue the operator of a firearms classified advertising website from which the killer illegally bought his gun after the U.S. Supreme Court on Monday declined to hear her appeal.

The justices left in place an April ruling by the Wisconsin Supreme Court that found that a federal law that shields website operators from liability for user content applied to Armslist LLC, the operator of Armslist.com.

Armslist is an Oklahoma-based website that allows users to post classified advertisements for firearms and related equipment. Potential buyers contact sellers directly.

The lawsuit, including several claims under Wisconsin law such as negligence and wrongful death, stemmed from a 2012 shooting at a beauty salon in Brookfield, Wisconsin. Gunman Radcliffe Haughton killed his wife, Zina Daniel, and two of her co-workers there before taking his own life. Four other people were injured in the shooting.