WASHINGTON — Labor leaders and businesses are closely watching a Supreme Court case to be argued Wednesday that involves a popular strategy used by unions to organize hundreds of thousands of workers.
That strategy — widely deployed by the Service Employees International Union and the Unite Here hotel workers union — involves pressuring an employer into signing a so-called neutrality agreement in which the employer promises not to oppose a unionization drive.
By some estimates, more than half of the recent successful unionization campaigns involve such agreements, which sometimes allow union organizers onto company property to talk with workers.
Benjamin Sachs, a professor of labor law at Harvard Law School, said the case before the Supreme Court was potentially “the most significant labor case in a generation.”
Mr. Sachs said that if the court ruled against labor, it could hobble significantly efforts by private-sector unions to organize workers.
He added that the other big labor case the Supreme Court has agreed to hear this session could have a significant effect on public-sector unions. In that case, a home-care worker has asked the court to rule that the state of Illinois violated her First Amendment rights by requiring her to pay “fair-share” fees, much like dues, to a union she did not support.
In the case being argued on Wednesday, an employee of Mardi Gras Gaming in Florida sued Unite Here, asserting that its neutrality agreement with the company was illegal. The 11th U.S. Circuit Court of Appeals ruled in his favor, finding that the agreement was a “thing of value” that federal labor law bars employers from giving to any union or union official.
The National Right to Work Legal Defense Foundation, which helped the Mardi Gras employee, Martin Mulhall, bring the case, said another prevalent union tactic — in which unions get employers to agree to use “card check” rather than a secret ballot election to determine whether a majority of workers want a union — should also be considered an illegal thing of value.
With card check, union organizers ask workers to sign cards saying they support a union and if a majority of workers sign them, the union presents the cards to the employer so the employer will recognize the union.
As part of its neutrality agreement, Mardi Gras Gaming agreed to permit card check. In exchange Unite Here pledged to back a casino gambling ballot initiative, spending more than $100,000 on the effort, and not to picket or strike Mardi Gras during its unionization drive.
Craig Becker, general counsel of the AFL-CIO, said the Right to Work group’s legal theory to bar such agreements “would criminalize a large swath of ordinary, voluntary labor-management relations.”
“Under their theory,” Mr. Becker said, “parties cannot agree to this, the employer can’t give it unilaterally, and the union can’t even ask for it. The implications are really sweeping.”
Mr. Becker argued that when Congress barred employers from giving union officials a “thing of value,” the legislation was intended to prohibit gifts such as Cadillacs that could improperly influence officials.
Mr. Becker said neutrality agreements should not be considered such corrupt “things of value” that the law addressed.