In the United States, a vehicle that is assembled in Canada or Mexico and is distributed domestically by a Big Three automaker is not considered a captive import. This is due to the integration of manufacturing operations by the Big 3 in these countries due to the hospitable trade environment created by the North American Free Trade Agreement (and before NAFTA, the US-Canada Auto Pact), coupled with the proximity of these nations to the U.S. Also, vehicles made and marketed by European automakers that were eventually acquired by the Big Three automakers, such as Land Rover, Volvo, and Saab, are generally not considered to be captive imports. The Opel vehicles sold in the 1960s and 1970s are exceptions to this rule because they were sold through the Buick distribution channel, while retaining the Opel brand name. Thus, they are captive imports.