Google’s robot just got its driver’s license.

On Tuesday, the federal agency that sets road rules — the National Highway Traffic Safety Administration — released a letter to the Internet giant that supports its interpretation of a driverless system as legally adequate for roadways, a key victory for the critical initiative within Alphabet, Google’s parent company.

Previously, the NHTSA only considered humans as drivers under law, because that’s how cars worked until Google came along. Now the agency has said it will consider Google’s self-driving system a driver, too.

The letter came in response to a November petition from Chris Urmson, the director of Google’s self-driving car project. Urmson argued that regulators should treat Google’s homemade cars, built without a steering wheel and brakes, on par with human drivers. It has been a persistent sticking point for the Google unit, particularly after California issued draft autonomous vehicle rules expressly prohibiting driverless cars.

Ensuring that its driverless fleet has regulatory approval to get on the roads is critical to Google’s car strategy.

The NHTSA letter isn’t a ruling; it’s a clarification about how the agency will interpret the law in the future. You can read the full thing here (warning: It’s a mess), but the key part is below:

As a foundational starting point for the interpretations below, NHTSA will interpret driver in the context of Google’s described motor vehicle design as referring to the SDS, and not to any of the vehicle occupants. We agree with Google its SDV will not have a driver in the traditional sense that vehicles have had drivers during the last more than one hundred years. The trend toward computer-driven vehicles began with such features as antilock brakes, electronic stability control, and air bags, continuing today with automatic emergency braking, forward crash warning, and lane departure warnings, and continuing on toward vehicles with Google’s SDV and potentially beyond. … If no human occupant of the vehicle can actually drive the vehicle, it is more reasonable to identify the driver as whatever (as opposed to whoever) is doing the driving. In this instance, an item of motor vehicle equipment, the SDS, is actually driving the vehicle.

Last month, Secretary of Transportation Anthony Foxx, who oversees the NHTSA, announced that his department would develop self-driving guidelines by June. Those guidelines would also agree with Google’s interpretation of driverless vehicles.

In 2012, Google hired Ron Medford, the NHTSA deputy director, to be the director of safety for its self-driving car program, an early signal of its ambition.