In a defeat for the union movement, the Supreme Court on Thursday struck down a first-in-the-nation law adopted in California that would have barred companies from speaking out against unions if they received state funds.

The justices in a 7-2 decision said the state measure conflicts with the free-speech zone created by federal labor law.

The ruling is likely to benefit especially companies in the healthcare industries, such as nursing homes, that receive some state funds and have low-level employees who are not unionized. It is a sharp setback for unions seeking to organize janitors, nurses, clerical workers and other employees in those areas.

Labor organizers may encourage workers to join unions, the high court said, but the employers also are free to try to persuade them against unionizing. Employers do not lose this right simply because they take the government's money, the justices said.

The California law was triggered by a campaign to organize janitors in the Los Angeles area. Mike Garcia, a union leader, complained to lawmakers that some companies were using state money "to pay for aggressive anti-union tactics."

State lawmakers, led by Sen. Gil Cedillo (D-Los Angeles), won approval of a bill to stop this practice. The measure, known as AB 1889, said state contractors and other private employers may not use state money "to assist, promote or deter union organizing."

The sponsors described this as the "nation's first state neutrality law" on labor organizing.