The case deals with the dusky gopher frog, listed as endangered in 2001, and whether the agency went too far in declaring a 1,544-acre tract in Louisiana “critical habitat” for the frog, even though it does not now live on the site. Fish and Wildlife determined the land has attributes of a place for the animal to live and should be categorized as critical habitat.

The landowners, which include Weyerhaeuser, challenged the agency’s decision. They planned commercial and residential development and timbering on the land.

A federal district court ruled in favor of Fish and Wildlife. In 2016, an appeals court upheld the lower court’s decision, prompting the landowners’ appeal to the Supreme Court.

At oral arguments, Justice Elena Kagan asked Bishop whether a modest change to another tract to make it suitable habitat for the frog would be acceptable. If requiring only minimal changes, Bishop said he wouldn’t rule it out. But he said, “That isn’t this case.” Kagan said the Endangered Species Act states “that habitat isn’t just sort of there and perfect always, that habitat requires things to be done to it” to protect wildlife.

Chief Justice John Roberts asked Kneedler whether there are any limits on the amount of required habitat restoration. Kneedler replied that “it has to be, according to [Fish and Wildlife], reasonable efforts.” Justice Samuel Alito asked, “Well, what’s the definition of reasonable?”