The fight to protect British Columbia's killer whales returned to court on Wednesday, as the federal government challenged a ruling that it has not adequately protected the endangered orcas.

The case was originally heard in 2010 in Federal Court, where a coalition of environmental groups successfully argued that the Department of Fisheries and Oceans flouted laws outlined in the Species at Risk Act, which requires the department to protect the identified critical habitats of endangered species.

The government was judged to have "acted unlawfully" by failing to implement sufficient measures to safeguard the whales' environment, but the government is now challenging the ruling, arguing that it has sufficient discretionary powers under the Fisheries Act to protect whale habitat.

"You need to protect critical habitat for species to survive, you just need to to do that, and anything that suggests it's optional to do that is just smoke and mirrors," Margot Venton, a lawyer representing several environmental groups, told CBC News.

Two populations of killer whales live off the B.C. coast — about 220 in the north considered "threatened" and another 85 or so in the south listed as "endangered."

The government wishes to maintain control over how it protects these endangered species but the environmental groups argue that means protecting much more than just the animals themselves.

In B.C., this would mean protecting the whales' source of salmon, which could have a significant impact on fish farms, commercial fishing and housing developments.

A similar case brought in 2009 saw environmental groups win unprecedented protection for B.C.'s endangered nooksack dace fish, after the Federal Court found the Fisheries and Oceans minister had violated the Species at Risk Act by failing to identify the habitat of the tiny fish.