In the case being argued on Wednesday, Unite Here Local 355 vs. Mulhall, an employee of Mardi Gras Gaming in Florida sued Unite Here, asserting that its neutrality agreement with the company was illegal. The United States Court of Appeals for the Eleventh Circuit 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.

Unite Here appealed, urging the Supreme Court to overturn the Eleventh Circuit and instead embrace rulings of the Third and Fourth Circuits, which have held that such agreements were not illegal things of value.

Karen Harned, executive director of the National Federation of Independent Business Small Business Legal Center, which filed a supporting brief with the Supreme Court, applauded the Eleventh Circuit and denounced neutrality agreements, asserting that they are the type of improper “thing of value” that employers are prohibited from giving to unions.

“A lot of small employers don’t have the resources to fight back if they’re the subject of a union campaign to get them to sign a neutrality agreement,” she said. “We are concerned that neutrality agreements are nothing more than extortion. The way they’re being used by unions, the unions say, ‘We promise not to trash your reputation or do X, Y, Z, if you sign this agreement.' ”

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.