LAS VEGAS (AP) — The unprecedented move from MGM Resorts International to sue hundreds of victims of last year’s mass shooting in Las Vegas relies on an obscure U.S. law never tested in court.

The casino-operator says the lawsuits are an effort to avoid years of costly litigation after the deadliest mass shooting in modern U.S. history. Experts believe the legal maneuver may not play out that way.

MGM isn’t asking for money but for courts to declare the company isn’t liable after a gunman killed 58 people and injured hundreds more from one of its casino-resorts.

Any protections hinge on a law enacted after 9/11 that requires an attack to be called an act of terrorism.

Experts believe a federal court may not be the appropriate entity to do that. The U.S. Department of Homeland Security said Friday that the law authorizes its leader to make that declaration.