The North American Automobile Trade Association has wasted no time linking yesterday's announcement of relaxed competition-exemption rules governing European car sales to its own developing cross-border dispute. A major row is developing between US car dealers and manufacturers who are trying to stop them buying cheaper cars in Canada for sale in the US. US dealers in border states are increasingly forced to do this to compete with independent dealers importing new Canadian vehicles and have been threatened with the withdrawal of warranties on Candian-sourced cars and, in Ford's case, cut allocations of the Thunderbird.