After 2015 Wall continued to keep a high profile on the national stage as a frequent critic of both Liberal Prime Minister Justin Trudeau and Alberta NDP Leader and Premier Rachel Notley. In 2015 Wall wrote a letter to Trudeau urging him to suspend the federal government's plan to resettle 25,000 Syrian refugees before the end of that year. He would go on to consistently target Trudeau over the federal carbon tax, laying the groundwork for the province to launch a constitutional challenge against the measure in April 2018. Wall was also critical of Notley's efforts to strengthen national efforts to address climate change, and by 2017 Saskatchewan and Alberta were engaging in a series of trade disputes that began when Wall publicly attempted to lure energy companies to move their headquarters from Calgary to Saskatchewan. Relations between the provinces were so dire at times that their respective trade ministers were not speaking.