On Wednesday, the U.S. Supreme Court will hear a complaint against Twitter Inc (TWTR.MX) by the American family of a Jordanian man murdered in an Istanbul nightclub massacre.

The family of an American lady slain in a Paris Islamic militant assault sued Google LLC-owned YouTube, part of Alphabet Inc (GOOGL.O), and the justices heard arguments in an appeal on Tuesday. Both cases sought damages from “an act of international terrorism” under U.S. law.

Nawras Alassaf’s relatives accused Twitter of supporting the Islamic State group, which claimed responsibility for the Jan. 1, 2017, attack that killed him and 38 others soon after midnight at a New Year’s party, by neglecting to control its accounts and tweets.

Twitter appealed after a lower court allowed the case to proceed and determined that the firm had failed to take “meaningful actions” to prevent the Islamic State’s use of the social media site.

On Tuesday, the nine justices in the case looked divided over whether to modify Section 230 of the Communications Decency Act, which shields internet businesses from a wide range of claims. Section 230 immunity prompted the lower court’s dismissal.

The family of Nohemi Gonzalez, an American woman killed in a 2015 Paris massacre by Islamic State, is suing Google for suggesting the group’s video to YouTube subscribers.

The 9th U.S. Circuit Court of Appeals in San Francisco did not evaluate whether Section 230 precluded the Twitter family’s complaint. Google and Facebook, both defendants, did not join Twitter’s appeal.

The family’s claims must argue that the firm deliberately supplied “significant support” to an “act of international terrorism” to allow them to sue under the anti-terrorism statute.

President Joseph Biden’s government supports Twitter, arguing that the Anti-Terrorism Act only applies to “offering broad help to a foreign terrorist group” with no causal relationship to the conduct. The government supported Tuesday’s plaintiffs. Islamic State claimed retribution for Turkish military engagement in Syria.

Police arrested Uzbek Abdulkadir Masharipov, the key suspect. Twitter has banned over 1.7 million accounts for “threatening or encouraging terrorism,” according to court documents. The lawsuits must be decided by June.