BISMARCK, N.D. — Being listed as a plaintiff in decades-old lawsuits doesn't mean that the environmental entity Earth First can be sued as an established group for opposing the Dakota Access oil pipeline, an attorney with the Center for Constitutional Rights says.

Pamela Spees in court documents filed Monday responded to a federal judge who last month demanded she explain what appear to be discrepancies in the center's argument that Earth First is an unstructured social movement or philosophy, similar to Black Lives Matter, and can't be sued.

U.S. District Judge Billy Roy Wilson pointed out that Earth First was a listed plaintiff in three federal lawsuits in the 1980s and 1990s. "If Earth First can sue, it seems to me that it is subject to being sued," he said.

Spees disagreed, saying that just because Earth First was listed as a plaintiff doesn't mean it actually had the legal right to be one.

"Earth First's capacity to sue does not appear to have been considered in any of the three cases," she said.

The lawsuits involved a water project in Arizona, a wilderness area in Oregon and a New Mexico canyon important to Native Americans.

Texas-based Dakota Access pipeline developer Energy Transfer Partners in August sued Earth First, Greenpeace and BankTrack for up to $1 billion, alleging they worked to undermine the $3.8 billion pipeline that's now moving oil from North Dakota to Illinois. The larger question of whether the lawsuit seeks to vindicate damage from criminal activity or is an attack on free speech is unresolved.

ETP lawyers maintain Earth First has been served with the lawsuit via Earth First Journal, a Florida-based environmental publication.

Spees, who represents the journal, says the publication and the movement aren't the same, and that neither can be sued.

"Earth First Journal's involvement in this case began only when plaintiffs decided to dump a copy of their complaint, addressed to Earth First, in the post office box of the Journal," she said.