On December 7, 2012 the Government of Canada released a policy statement and revised the guidelines for investments by State-Owned Enterprises in the Canadian oil sands. This policy statement was in response to the proposed purchase of Nexen by the Chinese SOE, CNOOC. According to the new guidelines, foreign investors must convince the Minister of Industry that a particular investment is likely to be of net benefit to Canada and those investments by foreign SOEs to acquire controlling interests in a Canadian oil sands company will be found to be of net benefit on an exceptional basis only. The purpose of this paper is to examine the impact of this announced policy change on the stock returns of firms operating in the oil sands. We employ an event study analysis to examine the impact of the policy change on the oil sands share price return after the announcement. We find that the announced changes to foreign investment in the oil sands significantly reduced stock returns in that industry and had a much larger negative impact on smaller oil sands companies (the juniors).