In Canada, as Today's Trucking has documented several times over the years, there have been precedent-setting labor decisions which have determined that independent owner operators and temporary agency drivers can be organized and made to be part of a labor union -- even against some workers' wishes.
Interestingly, though, the Teamsters' in the U.S. are backed by FedEx's main competitor, UPS, whose workforce is represented by the same union, nationwide.
Because 80 percent of FedEx's business is airfreight, the company, including its Ground division, operates under the Railway Labor Act (RLA), which requires a majority of votes from all a company’s employees in order for that firm to be unionized.
UPS, instead, is governed by the New Deal-era National Labor Relations Act, which has significantly lower barriers to labor organizing.
After trying unsuccessfully in the 1990s to be reclassified under the RLA (a move that rival FedEx reportedly supported), the Teamsters and Big Brown, with much higher labor costs than its competitor, are lobbying Democrat-controlled Congress to have FedEx's ground operations switched to the National Labor Relations Act as well.