The U.S. Supreme Court hears arguments Monday in an ominous case threatening the ability of workers to bargain collectively for fair wages, benefits and job conditions, the latest assault on unions financed by some of America's richest families and corporations.

Janus v. AFSCME Council 31 challenges the right of public sector unions to collect “fair share” fees from nonmembers for the basic costs of bargaining and contract enforcement, services that benefit them and dues-paying members alike.

Tens of thousands of IBEW members are among millions of public sector workers nationwide whose collective voice at work is threatened by the lawsuit.

“This case is one of the most important cases to corporate interest groups. It is one of the cases that made Senate Republicans so determined to block President Obama’s nominee to the Supreme Court,” said Celine McNicholas, chief labor attorney for the Economic Policy Institute. “The outcome of Janus will affect millions of working people across the country and will impact the public services we depend on these workers to provide.”

EPI reported this week on the money trail behind Janus, as well as two similar Supreme Court cases since 2012, each of which attacked fair share fees.

“Litigating a case all the way to the United States Supreme Court is expensive: years of attorneys’ fees, court costs, and trial expenses add up,” the report states. “How is it that a few public-sector employees who seek to challenge union representation are able to shoulder these costs?”

The answer is pro-bono, with anti-union nonprofits footing the bill. The Liberty Justice Center and National Right to Work Legal Defense Foundation are bankrolling Janus. The Center for Individual Rights financed Friedrichs v. California Teachers Association in 2015 and the National Right to Work Legal Defense Foundation covered the costs of Harris v. Quinn in 2012.

Through a meticulous review of publicly available IRS data, EPI traced the major foundations that underwrite those organizations and key donors – generally family and corporate trusts – that support the foundations. Notable names include the Kochs, Mercers and Waltons, all billionaire families who regularly back Republican and conservative causes.

By funneling money to groups that fight the 1 percent’s battles, donors on EPI’s lists are financing the Supreme Court cases whether they intended to or not.

But many donors’ enmity toward unions is no secret. The Koch brothers – with a combined net worth of nearly $100 billion – and Walmart’s Walton family are notoriously anti-union. And then there’s the DeVos family.

A nonprofit called Donors Trust has contributed to all the groups financing fair share cases the past six years. Donors Trust’s backers include the Richard and Helen DeVos Foundation, built from their Amway fortune. The couple’s daughter-in-law is Secretary of Education Betsy DeVos, a brazen critic of teachers’ unions.

Her husband, Dick DeVos Jr, is virulently anti-union on all fronts. In 2012, he spent millions crusading against a pro-union initiative in Michigan. When it failed, he orchestrated a lightning-fast campaign to pass right-to-work, which the state’s Republican-controlled legislature did exactly one month later.

Despite EPI’s exhaustive work digging up the money trail, researchers say much is still unknown. “It remains difficult to develop a clear picture of the complete financial landscape of these cases,” the report stated. “What is clear is that a core group of foundations with ties to the largest and most powerful lobbies representing corporate interests have provided consistent financial support for the fair share fee cases.”

But one thing very clear, the EPI study said, is the danger Janus poses to all workers:

“In a political system dominated by moneyed interests, workers are left with little power if they do not have an effective mechanism to pool their resources. It is profoundly undemocratic to elevate the objections of a minority over the democratically determined choices of the majority of workers.

“This principle is what is at stake in Janus. The decision in this case will determine the future of effective unions, democratic decision-making in the workplace, and the preservation of good, middle-class jobs in public employment.”

The Economic Policy Institute published a list of donors to the groups financing the anti-union attacks at the Supreme Court. The document is embedded below: