It's been a long time coming, but today it arrived: a lawsuit provoked by the federal government's amendments to the Yukon Environmental and Socio-Economic Assessment Act (YESAA).

Three Yukon First Nations — the Teslin Tlingit Council, the Champagne and Aishihik First Nations, and the Little Salmon/Carmacks First Nation — filed a petition in Yukon Supreme Court on Wednesday.

Yukon chiefs have vigorously resisted the amendments to YESAA, since Bill S-6 was introduced in the Senate just over a year ago.

They have said the changes violate their land claims agreements, in particular, four controversial amendments that were introduced at the end stages of the consultation process.

"The amendments through Bill S-6 undermine or weaken Yukon's development assessment process and our role as Yukon First Nation governments," said Teslin Tlingit Council chief Carl Sidney.

"They are a clear breach of our final agreements."

Little Salmon Carmacks chief Eric Fairclough said the final agreements are "constitutionally protected" and said First Nations in the Yukon will resist moves by Stephen Harper to "undermine environmental legislation throughout Canada."

The petition was accompanied by affidavits from a total of 11 Yukon chiefs. Fairclough says all First Nations which belong to the Council of Yukon First Nations are helping to pay for the cost of the lawsuit.

Sidney says Yukon First Nations made "huge compromises" to ensure that they have joint management of lands and resources. He says the amendments to YESAA dilutes the the role of First Nations, and they will not accept that. 

Gregory McDade, with the Vancouver firm of Ratcliff and Company, said the suit takes exception to "both the process and the principle" of the changes brought about by S-6.

McDade said a case management conference is set for December. He added that the Yukon government may become a respondent if it chooses. 

Both the federal government and the Yukon government have maintained that the amendments cannot affect the integrity of the final agreements, saying that in the case of a dispute between YESAA and the final agreements, the agreements will prevail.

McDade says that assessment is "wrong." The lawsuit says "no law enacted by Canada or Yukon is enforceable if it is in conflict or inconsistent with a Final Agreement."

The lawsuit goes on to claim that the amendments "unlawfully permit unilateral delegation by Canada to Yukon of powers and responsibilities."

Both the NDP and the Liberal candidates have said their respective parties would repeal the problematic amendments.

This filing comes just days before the federal election on Monday. The Yukon chiefs say that is simply a coincidence.

Yukon Conservative incumbent Ryan Leef has supported the passage of Bill S-6. He declined to comment on the court action.

On mobile? Read the First Nations' court petition here