The families of the victims of the deadly 2017 fire in London’s Grenfell Tower are fighting back against claims that the litigation should be thrown out of U.S. federal court. The dispute marks the plaintiffs’ first major hurdle in what is expected to be a tenaciously litigated case.

In late August, Arconic, Saint-Gobain Corp. and Whirlpool filed a motion to dismiss the lawsuit, arguing that the plaintiffs failed to make legal claim under either Pennsylvania or English law, and improperly sued the U.S.-based companies, while failing to join the necessary foreign entities.