The United Auto Workers say Tesla CEO Elon Musk allegedly broke national labor laws by tweeting.

A complaint dated Wednesday and filed with the National Labor Relations Board says Musk violated the National Labor Relations Act when he sent out a tweet the union alleges threatened to take away stock options from any employees attempting to unionize.

Here is the tweet the complaint refers to:

Musk

"Elon's tweet was simply a recognition of the fact that unlike Tesla, we're not aware of a single UAW-represented automaker that provides stock options or restricted stock units to their production employees, and UAW organizers have consistently dismissed the value of Tesla equity as part of our compensation package," Tesla said in a statement. "We fundamentally believe it's critical that all employees be owners of Tesla so that everyone is on the same team, with all sharing in the company's success."

Musk did later send out a tweet saying that he believes the UAW does not "have individual stock ownership as part of the compensation at any other company."

Musk2

"The UAW does not have a policy preventing employees from owning stock options," UAW spokesman Brian Rothenberg told CNBC.

Download the full NLRB complaint here.