By Lisa Johnson Alberta’s bill lowering the bar for a separation referendum has spurred a First Nation to push ahead with a legal challenge against the premier’s flagship sovereignty act. Danielle Smith has said her Alberta Sovereignty Within a United Canada Act is needed to push back on what the province believes is unconstitutional federal encroachment into provincial jurisdiction. But Onion Lake Cree Nation Chief Henry Lewis said that law has always been about undermining federal authority and asserting provincial control, which goes against his community’s Treaty 6 relationship with the Crown. “I want to respectfully remind the premier that this land that we stand on today is treaty land and is not yours to take or make sweeping decisions about,” he said at a news conference in Edmonton on…