MEMPHIS, Tenn. — FedEx Ground has sent a letter to 12,000 independent contractors notifying them of new business standards they must comply with.

According to Dow Jones, which obtained a letter from the delivery giant to its contractors, the workers risk losing their contract if they don’t abide by the new rules.

FedEx Ground has been battling efforts unionize independent drivers.

Backed by rival UPS, the Teamsters are lobbying Congress to change how the company is governed under federal law, making it easier to unionize. The union is also trying to get FedEx’s independent drivers to be recognized as company employees.

There is also a larger movement in the U.S. — which is strongly supported by the Obama administration — to crack down on companies that supposedly misclassify workers as independent contractors.

Contractors can no longer organize as partnerships or sole proprietorships; they are now required to incorporate under state law. Owner-operators are also required to treat their personnel as employees, according to Dow Jones.

Last year, FedEx won an appeal overturning a National Labor Relations Board regional ruling regarding FedEx Ground Home Delivery terminals in Massachusetts. A jury in Washington State also agreed that the drivers were contractors in a class-action suit.

In Canada, the Teamsters are also targeting FedEx truck and van delivery drivers for unionization.

— with files via Truckinginfo.com