The U.S. Department of Labor’s web site refers to the National Labor Relations Act, passed in 1935, as “labor’s Magna Carta,” extolling the fact that the act guarantees “workers the right to organize and bargain collectively.”

That right could be history for millions of America’s workers in the wake of a recent decision by the National Labor Relations Board (NLRB) that sharply limits union eligibility. The decision goes well beyond a blow to unions: it could result in a more polarized economy and a less democratic society.

The origin of the current ruling can be found in a 2001 U.S. Supreme Court decision — the Kentucky River case — in which the court bounced back to the NLRB the issue of what defines a supervisor.

In a partisan 3-2 decision in the Oakwood Health Care case, all Bush appointees to the board voted to redefine “supervisor” far more broadly. Instead of those old-fashioned criteria such as hiring, firing and promoting other workers, this new ruling says that someone can be classified as a “boss” when they do a modest amount of coordination, say assigning a worker to the night shift. And they only need to perform these “supervisory” duties as little as 10 percent to 15 percent of the workweek.

Overnight, millions of Americans could find themselves “promoted” to supervisory ranks. A little reassigning, a little independent thinking and presto — you’ve climbed the job ladder. Before clinking the champagne glasses, however, it’s best to remember that the reward is not a fatter paycheck but the loss of a fundamental labor right: union membership.

The two remaining Clinton board members both strongly dissented, pointing out that the decision stranded many workers in an employment “twilight zone”: “workers who have neither the genuine prerogatives of management, nor the statutory rights of ordinary employees.”

While the Oakwood Health Care case deals with nurses, this expansive definition of supervision could impact many workers, from professionals such as computer programmers to blue-collar stalwarts such as toolmakers. The board dissenters point out that by 2012 nearly one out of four employees — 34 million — could be classified as professionals, an area particularly subject to this reclassification.

Throughout the economy, new forms of work organization and new forms of information technology are giving workers increased input on the job. It is ironic, not to say undemocratic, to think that more input could result in fewer rights. The result could be a back to the future scenario where we return to the labor protections of the early 1930s as we enter the 21st century.

This decision reflects a broader pattern in which recent NLRB rulings undermine the intent of the National Labor Relations Act. Instead of facilitating “the right to organize and bargain collectively,” the NLRB has eliminated it for graduate teaching assistants, temporary workers and the handicapped, among others.

For all too many workers, joining a union represents a risk rather than a choice. Twenty-three thousand workers a year are disciplined or even terminated for union activity, about one worker every 23 minutes, according to American Rights at Work, a labor policy organization.

Union membership has fallen from about 35 percent of the workforce in the mid-1950s to less than 8 percent in the private sector today. Big corporations have become more powerful than ever while unions have been sharply downsized.

Even before the current NLRB ruling, Human Rights Watch sharply criticized the exclusion of millions of workers from union coverage and found that U.S. labor law failed to meet human rights norms in critical areas.

As worker rights are being dismantled, we have become a far more polarized economy.

U.S. workers are in the midst of the first expansion in 60 years in which worker paychecks are being bypassed. As union membership has continued to shrink, so have worker wages. The wages of nonmanagement employees, adjusted for inflation, have slid 10 percent since the beginning of the 1970s.

In the past, unions have linked rising productivity to higher wages and better benefits, paving the road to the middle class. These gains fueled purchasing power throughout the economy, stimulating economic growth.

More than paychecks are at stake. Unions also have given voice to worker concerns on the job. In the case of nurses, nearly 60 percent told a recent survey that unions provide a way to improve patient care by insuring a formal channel to press for adequate staffing and better equipment. When nurses lose this channel, patients often pay the price.

Limiting unions in the workplace also mutes their voice politically, corroding the checks and balances vital to a democratic society. Who then speaks for the broader interests of working families on issues from the minimum wage to health care?

At issue is workers retaining the right to decide who represents them. By eliminating this choice, the labor board’s decision weakens unions today and undermines democracy tomorrow.

Harley Shaiken is a professor at the University of California, Berkeley, specializing in labor and the global economy, and author of many books and articles on the U.S. workforce. This article is reprinted from the AFL-CIO’s online Point of View (