A federal appeals court has affirmed a lower court’s dismissal of litigation filed against Twitter Inc., Google LLC and Facebook Inc. by victims and family members of victims who were among the 49 people killed and 53 injured in the 2016 Pulse nightclub shooting.

“We sympathize with Plaintiffs — they suffered through one of the worst terrorist attacks in American history,” but terrorist attacks present unique difficulties for those injured because the terrorists responsible may be beyond the court’s reach, says Tuesday’s ruling by the 6th U.S. Circuit Court of Appeals in Cincinnati in Earl Crosby et al. v. Twitter Inc.; Google LLC; Facebook Inc.

The gunman in the June 2016 attack, Omar Mateen, had pledged allegiance to the Islamic State group before police fatally shot him after the attack.

The litigation was filed in U.S. District Court in Detroit in December 2016. The District Court dismissed the case, which the 6th Circuit affirmed in Tuesday’s ruling.

Plaintiffs provide examples of how IS posts on the defendants’ websites recruited more than 30,000 foreigners to join IS, and how after the attack IS praised Mr. Mateen and identified him has an Islamic State fighter, said the ruling.

Plaintiffs “cannot hold defendant’s directly liable for their injuries unless there is some causal relationship between Defendants’ conduct had the Pulse Night club shooting,” said the ruling. Under the federal Anti-Terrorism Act, a proximate cause is required to establish liability.

“Plaintiffs ask us to define proximate cause as something less than requiring a ‘direct link,’” said the ruling.

If “we accepted Plaintiffs argument, Defendants would become liable for seemingly endless acts of modern violence simply because the individual viewed relevant social media content before deciding to commit the violence.”

Plaintiffs “allege no facts connecting Defendants to Mateen or the Pulse Night Club shooting. At most, Plaintiffs allege facts that generally connect Defendants to ISIS. But as the Amended Complaint admits, Mateen — and not ISIS — caused Plaintiffs’ injuries,” said the ruling in affirming the lower court’s dismissal of the case.

Plaintiff attorney Keith L. Altman, lead counsel at Excolo Law PLLC in Southfield, Michigan said, “We’re disappointed in the ruling, and we believe the ruling flies in the face of Congress’ intent” with respect to the Justice Against Sponsors of Terrorism Act.

“We have every intention of continuing to pursue it for cert to the Supreme Court,” he said.

A Twitter spokesman had no comment, while spokesmen for Google and Facebook did not immediately respond to a request for comment.