A car’s legal driver doesn’t always have to be human, according to U.S. vehicle safety regulators—it can also be artificial intelligence.

The National Highway Transportation and Safety Administration told Google that the artificial intelligence system that controls its self-driving car can be considered a driver under federal law. The legal interpretation by federal regulators was made in response to a November petition from Chris Urmson, the director of Google’s self-driving car project.

This is a critical first step for Google towards commercializing self-driving cars—a goal it wants to meet by 2020. However, NHTSA’s interpretation doesn’t mean fully autonomous vehicles are legal for public use. The next question is whether and how Google goog could certify that the self-driving system meets a standard that currently applies to vehicles with a human driver, says NHTSA’s chief counsel Paul A. Hemmersbaugh in a letter. This, in turn, leads to the next obvious hurdle: NHTSA must first test or find some way to verify such compliance.

In other words, a long regulatory road remains ahead.

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Google faces a regulatory and design Catch-22. The company designed a prototype self-driving car that has no steering wheel, throttle or brake pedals. Instead AI software controls the car. Lasers, radar, and sensors give the vehicle’s brains a 360-degree view of its environment to the point that it can recognize objects up to two football fields away.

Google believes that its AI self-driving system will consistently make the smartest, safest decision for the occupants of the vehicle as well as pedestrians or other users sharing the road; safer than even a human driver. And so the company is worried that giving human occupants of the vehicle mechanisms that controls things like steering, acceleration, braking or turn signals is actually detrimental to safety because it can override the safer decision made by AI.

And yet, right now, self-driving cars cannot be tested on public roadways without brakes, an accelerator, or a steering wheel that lets humans take over if necessary. Preliminary rules in California—where Google is headquartered and does the majority of its testing—prohibit the use of fully autonomous driverless cars that lack a steering wheel or a brake pedal.

To see Google’s self-driving car get pulled over, check out the following Fortune video below:

Google continues to push ahead despite looming legal questions. The company started working on self-driving technology in 2009. Initially, it modified Lexus RX450h SUVs and tested the vehicles in closed courses, and eventually on public roads near its Mountain View, Calif. headquarters. The company later introduced a prototype driverless car in June.

Today, Google is using 22 modified Lexus RX450h SUVs and 33 prototypes of its own design. The company began testing in Austin, Texas in July and announced this month that it would expand to Kirkland, Wash.