The recent decision by the National Labor Relations Board (NLRB) refusing to recognize a labor union for football players at Northwestern University is the latest manifestation that the American labor movement is troubled these days. The sacking of the union movement at Northwestern reflects that the scoreboard has tilted markedly against unions and workers as Minnesotans join the rest of the nation in celebrating the 122nd Labor Day, the unofficial end of summer.

The NLRB ruling is only a minor blip, but it is consistent with recent and prospective court rulings diluting the importance and impact of labor unions in protecting the rights of their employee members. However, some glimmer of hope is on the horizon for unions and their members, especially here in Minnesota.

The reduction in union membership and a corresponding diminution of unions' clout have been well-noted and analyzed. The receding number of labor union members has been attributed to a number of features, including the decline of manufacturing and other heavy industries, the growth of technology and in-home or off-premises work, the changing nature and complexion of the workforce, some heavy-handed governmental laws and regulations, and blunders by organized labor, among other factors.

Whatever the reasons, the results are stark. Union membership was nearly nonexistent when Labor Day originally was recognized, first by a few municipalities and states and then becoming a national holiday — the first Monday in September — in 1894. But unions expanded to encompass about one-third of the nonagricultural, salaried workforce by the post-World-War-II era. The growth was fueled by favorable legislation in the New Deal era of the 1930s and a growing economy after the war.

Over the past 50 years, however, unions have experienced an incredible shrinking base, with current membership around the country hovering at about 10 percent of the workforce, down by almost 25 percent in the last decade alone. Not only is membership in steep decline, but the retrenchment obscures the composition of union membership, which consists of only about 7 percent of employees in private enterprise, with the balance public-sector workers. This represents a large shift from the halcyon days for organized labor from the 1940s to 1960s, when the bulk of union members worked for private businesses.

The membership rolls have not reflected such problematic or precipitous decline in Minnesota. This state has the 13th-largest organized section in the country, about 14 percent of the workforce, comprising some 380,000 workers, a figure that has remained relatively steady in the past couple of years, although a slight reduction since 2008. In comparison, in neighboring Wisconsin, where public-sector unions continue to experience ongoing political strife, organized labor consists of only about 12 percent of the workforce, a dramatic 20 percent drop in the past two years alone.

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The nuances of their numbers do not tell the whole story. Besides the business, economic and social factors contributing to the declining union base, several court rulings have played a role in their plight, and one more may be forthcoming soon.

The U.S. Supreme Court during the last decade under Chief Justice John Roberts has not been very union-friendly. To the contrary, its holdings have been downright hostile.

During its recently concluded 2014-15 term, the high court reversed a lower-court ruling allowing retirees to receive post-retirement health insurance paid for by their employers, which had been negotiated for them by their union before their retirement. The court, in a decision written by Justice Clarence Thomas, overturned that decision and sent the case back for new proceedings because the labor union contract was silent as to the continuity of such benefits for retirees after expiration of the agreement.

Among other setbacks for the union movement: In 2014, the court disallowed President Obama to exercise constitutional authority to fill vacancies on the NLRB, the agency overseeing management-labor relations at the federal level, which had been held up for years by Republicans in Congress.

But a more stunning (and, perhaps, foreboding) ruling was the court's decision last spring allowing home health care workers in Illinois to refuse to join a union — or pay dues to it — even though the union represents them in collective bargaining with the state, which pays their wages. The court reasoned in Harris vs. Quinn that the First Amendment rights of freedom of expression and association trump the state law allowing unions to collect dues from these quasi-public-sector employees.

The ruling sent shudders through the labor movement, fearful that it may portend the dismantling of the framework of public-sector unionization, its real growth industry. That concern may be materializing as the high court in this term (which begins next month) will consider a comparable challenge by a group of California teachers to the so-called "agency shop" law in their state — and about two dozen others, including Minnesota — requiring certain public-sector workers to belong to and pay for unions to represent their interests. The challengers are making essentially the same arguments as the health care aides in the Illinois case, and many observers expect (and unions fear) a similar outcome.

That result could be debilitating to unions, especially in the public sector. Allowing workers to refrain from paying any dues undermines the financial foundation of unions, while allowing employees to obtain the benefits of union collective bargaining and other representation. But even that benefit may be diluted if the number of "free-riders" leads to diminishment of union coffers to support the efforts undertaken collectively on behalf of workers. Moreover, the practice could also be extended to the private sector, creating havoc for those unions as well.

But to reach that outcome requires the justices to overcome a significant hurdle. A 1977 decision of that tribunal in Abood vs. Detroit Board of Education upheld compulsory union membership for public-sector workers, while allowing them to "opt out" only of the limited portion of their dues that are used for political or ideological purposes. That system, known as "fair share," has been in existence now for nearly 40 years and forms a daunting barrier for the majority of the Roberts Court to set aside their proclaimed fidelity to judicial precedent.

But don't count on it. In dissenting in a patent case this June, Justice Samuel Alito, who wrote the Illinois home health care case, asserted that a long-standing precedent of 50 years be overturned. He opined that while precedent is "important … so are correct judicial decisions." His disinclination to follow established law was shared by two of his colleagues, Roberts and Thomas. If their view is adopted by two others on the bench, unions face the prospect of not being able to collect dues from all of the workers they purport to represent, which would constitute a significant blow to their vitality.

In another case, the justices have agreed to review this fall a $5.8 million class-action judgment for overtime pay to production workers at a meat-processing plant in neighboring Iowa. If decided adversely to the claimants, as a number of court watchers suspect, the case could erode the rights of employees, especially low-wage workers who comprise a prime target of union organizing today, to secure a remedy when forced to work more for less pay.

But a pair of developments in the District of Columbia last month is more encouraging. The NLRB ruled that businesses may be responsible for complying with minimum-wage and overtime laws for temporary workers they hire from outside agencies, which also could be extended to franchises, especially in the fast-food industry. Further, a federal appeals court in the nation's capital upheld the Department of Labor's extension of those wage requirements to some 2 million home health care aides, including thousands in Minnesota.

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These developments are welcome here in Minnesota, when management-labor relations are not as stormy. The relatively steady base of union membership creates greater stability. There have not been as many unfavorable court rulings here, nor any draconian legislation impairing unions' existence or impeding their growth, as in Wisconsin and a few other Midwestern states.

But the vicissitudes of litigation and the possibility of more politically motivated attacks create stormy threats that could rain on unions' parade here in Minnesota. That's why the forecast for unions and their numbers this Labor Day is partly cloudy.

Marshall H. Tanick is a Twin Cities employment and labor law attorney.