The National Labor Relations Board, the main federal labor law enforcement agency, ruled Tuesday that student assistants are employees covered by the National Labor Relations Act and therefore eligible to form a union.

The ruling could have a profound impact on higher education, as student assistants are widely used at private colleges and universities in lieu of traditional teachers.

The labor board ruled 3-1 in a case called Columbia University that student assistants are statutory employees covered by the National Labor Relations Act. The United Auto Workers has been seeking to represent both graduate and undergraduate teaching assistants there since December 2014. The labor board's ruling reversed a 2004 precedent called Brown that said graduate students were not employees. The current majority said that was no longer tenable.

"We hold today that student assistants who have a common-law employment relationship with their university are statutory employees under the act. We will apply that standard to student assistants, including assistants engaged in research funded by external grants," the majority said.

In an acknowledgement that the ruling would be controversial, the board's announcement made a point of saying that it has the authority to make the policy change because it is the primary arbiter of who the labor rights act's protections extend to. "Federal courts have made clear that the authority to define the term 'employee' rests primarily with the board absent an exception enumerated within the National Labor Relations Act. The act contains no clear language prohibiting student assistants from its coverage. The majority found no compelling reason to exclude student assistants from the protections of the act," it said.

The ruling was by Chairman Mark Gaston Pearce and Democratic members Kent Y. Hirozawa and Lauren McFerran.

Philip A. Miscimarra, the board's lone Republican member, dissented. He disputed that the board had the authority that it claimed. "The Supreme Court has stated that 'the authority structure of a university does not fit neatly within the statutory scheme' set forth in the NLRA," he said.

Labor unions have been trying for years to organize teaching positions at colleges. The United Auto Workers, while primarily a union of auto industry workers, has been one of the most aggressive in that effort. "Our union and hard-working graduate employees at some of our nation's premier universities have never wavered in our pursuit of workers' rights for tens of thousands of workers abandoned by the Bush-era Brown University decision in 2004," said Julie Kushner, director of UAW Region 9A.

Sen. Ben Sasse, R-Neb., a former president of Midland University, slammed the decision. "This misguided, politically driven decision rewrites the law by changing the meaning of words that were passed by Congress. That's not the NLRB's job. The ruling misunderstands both the nature of representative government and the teacher-student relationship: labor laws should be debated by the American people's representatives in Congress," he said.