What is Uber? The company’s standard answer is that it is a technology company—an app that matches people who want to get somewhere to people who will take them there for money. This is not wrong.

But, as the European Union’s highest court told the company on Wednesday, that answer is incomplete. Whether Uber likes it or not, it is, officially speaking, a transportation company.

The consequence of this designation is that, within the borders of the EU, the company will be regulated just like any other transportation company. That’s a big deal. It’s a big deal for Uber (which will now have to play by any rule a European city sets for transportation companies) and it’s a big deal for the platforms that, like Uber, depend on the labor of people who aren’t full-time employees.

First, the implications for Uber: The ruling “places a significantly larger regulatory burden on Uber, if they want to operate in any European city, and it also can severely restrict their growth, depending on the city,” says Arun Sundararajan, a professor at NYU’s Stern School of Business and the author of The Sharing Economy: The End of Employment and the Rise of Crowd-Based Capitalism. How might it prevent Uber from growing at the rate it has in the past? If, for example, a city has or imposes a cap on the number of professional drivers permitted within its limits, that cap would apply to Uber. The same goes for any city’s law requiring that drivers must be considered employees and not contractors, which would force Uber to either get out of town or make sure its drivers are classified properly.