Labor prosecutors are challenging Amazons long-running claim that it doesnt employ the massive network of drivers who deliver its packages across the country.

A regional director for the National Labor Relations Board has determined that Amazon is really a joint employer alongside one of its delivery contractors, an agency spokesperson said Thursday. The director also found that the e-commerce giant broke the law by making illegal threats, holding anti-union captive audience meetings and refusing to bargain with workers.

Although the case involves just one firm that Amazon contracted with in California, it has big implications for Amazons labor model in the U.S.

Even though Amazon delivery drivers work out of Amazon-branded vans and wear Amazon-branded uniforms, the company has long maintained that they dont actually work for Amazon but for one of its contracted firms, known as a delivery service partner (DSP). If Amazon doesnt employ the drivers, then it isnt responsible for meeting wage and safety standards or bargaining with those who want a union.

A finding that Amazon is a joint employer alongside its DSP could make the company responsible for any labor law violations and, in theory, force it to the bargaining table.

The case is still in its early stages and could eventually go before the five-member labor board in Washington.