The Supreme Court of Canada has ruled that investors can proceed with a lawsuit against Lundin Mining Corp. for failing to promptly disclose a significant rockslide at its Chilean mine. This decision clarifies the obligations of public companies to inform shareholders about material events. On Friday, the court overturned a lower court's ruling that had narrowly defined what constitutes "material information." This previous interpretation would have barred investors from filing a class action against Lundin for allegedly delaying the announcement of the rockslide. In October 2017, Lundin Mining identified instability in the walls of its open-pit Candelaria copper mine in Chile. Shortly after this detection, approximately 700,000 metric tons of waste material collapsed within the mine. Lundin did not disclose the incident until November 29, when it announced a 20 percent reduction in its production outlook for 2018. Following this disclosure, Lundin's stock price dropped by 16 percent, resulting in a loss of over $1 billion in market capitalization. Doug Sarro, an assistant law professor at the University of Ottawa, commented on the ruling, stating, "The Supreme Court has upheld the guidance that it’s given public companies in the past, which is when something internal happens within your business and it’s something important to investors, you should disclose that immediately." He noted that there had been discussions suggesting that companies need not disclose material changes unless they threaten the business's survival. Michael Thom, managing director of CFA Societies Canada, which participated in the case, expressed that the ruling is beneficial for both investors and the market. He stated, "This is good for investors, and this is good for markets. It doesn’t take the law in a new or difficult-to-understand direction." A representative for Lundin Mining indicated that the company would not comment on the Supreme Court's decision. The case began when investor Dov Markowich, who purchased Lundin shares after the rockslide but before the public announcement, sought to file a lawsuit under Ontario's Securities Act. Initially, the Ontario Superior Court of Justice dismissed his motion, but the Ontario Court of Appeal later reversed that decision, prompting Lundin to appeal to the Supreme Court. This ruling emphasizes the importance of timely disclosure by companies to their investors, reinforcing the legal expectations surrounding material information in the financial markets.