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 on provincial jurisdiction. But Onion Lake Cree Nation Chief Henry Lewis says it undermines his community’s pre-existing treaty with the Crown. He announced the legal challenge is moving forward a day after Smith’s government passed a bill significantly lowering the threshold for citizens to prompt a referendum, including one on seceding from Canada. The First Nation filed a statement of claim in 2022, but lawyer Robert Hladun says the community put it on pause,…