Since 1997, the Justice Department has prosecuted seven cases of slavery in the Florida agricultural industry — four involving tomato harvesters — freeing more than 1,000 men and women. The stories are a catalogue of horrors: abductions, pistol whippings, confinement at gunpoint, debt bondage and starvation wages.

Thankfully, those enslaved workers may be among the last found in Florida’s tomato fields. Today, virtually all Florida tomato growers have joined the Fair Food Program, which includes a code of conduct outlawing debt bondage and requiring humane conditions of labor and a more livable wage. Shade stations, toilets and drinking water are appearing in the fields, and educators are spreading word about the code to the harvesters.

This miracle didn’t come about overnight. The Coalition of Immokalee Workers (CIW), an organization of migrant workers based in Immokalee, Fla., has strived for 19 years to upgrade working conditions and eradicate slavery in the state’s tomato industry. Pressure on growers, whose profit margins have shrunk over that period, was only marginally successful; growers feared that pay increases raising the price of tomatoes would drive buyers to Mexico or other places for cheaper produce. But when the coalition changed tactics and demanded that tomato buyers join the Fair Food Program, reforms came thick and fast. Profitable and image-conscious retailers, pressed by consumers and civil society groups, saw the market and publicity benefits of ethical buying practices.

Over the past seven years, the food service industry and fast food restaurants have come on board, promising to purchase tomatoes only from growers who agree to comply with the code of conduct. What’s more, the buyers pledged to pay a penny-a-pound premium for every box of tomatoes they purchased from participating growers, who pass on the increase to their workers.

An indispensable aspect of the agreement is the Fair Food Standards Council, an independent monitoring body supported entirely by private donations and grants. The council investigates complaints of sexual harassment, wage disputes and other code violations. Its enforcement is what makes the program work: Without it, the code is simply a statement of good intentions. Growers who violate the code can be ejected from the program, denying them access to a growing market of buyers for Florida’s fairly picked tomatoes that includes food chains such as Subway, McDonald’s and Burger King and grocers such as Whole Foods, Aramark and Compass.

International Justice Mission, a nonprofit human right organization — for which I work — that locates and rescues bonded labor slaves in South Asia has an additional reason to support the initiative. The State Department’s diplomatic efforts to combat slavery in the countries where the International Justice Mission works are much-needed, but they’re undermined if the United States tolerates exploitative labor practices at home. Getting our house in order with regard to modern-day slavery would show other nations that we’re serious about this problem.

The CIW model is one of the great human rights success stories of our day. But the Fair Food Program won’t be sustainable unless the largest buyers of tomatoes — grocery stores — reward the growers in the program with their purchases and pay the price premium. Despite years of pressure from the CIW and from consumers, major supermarket chains including Ahold, Kroger’s and Publix have snubbed the Fair Food Program. They prefer their private production codes, which don’t benefit from the Fair Food Standards Council’s independent monitoring and evaluation.

But these private buyers aren’t the only major purchasers of Florida tomatoes who have yet to sign on to the Fair Food Program. President Obama should set an example to private buyers by announcing that from now on, the tomatoes the U.S. Agriculture Department purchases for the school lunch programs and for market stabilization will be purchased from the Fair Food Program.

This Labor Day, like every other day, the world’s most exhausting, dangerous, poorly paid and degrading jobs are being performed by the world’s most impoverished and vulnerable people. But that is not true anymore in Immokalee. The Coalition of Immokalee Workers has changed Florida and U.S. agriculture for the better. May their brilliant model flourish and inspire producers, buyers, consumers and workers in every industry where labor slavery persists.