San Francisco, land of unrestrained tech wealth and the attendant hoodies and $29 loaves of bread, just said whoa whoa whoa to delivery robots.

The SF Board of Supervisors voted on Tuesday, December 5 to severely restrict the machines, which roll on sidewalks and autonomously dodge obstacles like dogs and buskers. Now startups will have to get permits to run their robots under strict guidelines in particular zones, typically industrial areas with low foot traffic. And even then, they may only do so for research purposes, not making actual deliveries. It’s perhaps the harshest crackdown on delivery robots in the United States—again, this in the city that gave the world an app that sends someone to your car to park it for you.

Actually, delivery robots are a bit like that, though far more advanced and less insufferable. Like self-driving cars, they see their world with a range of sensors, including lasers. Order food from a participating restaurant and a worker will load up your order into the robot and send it on its way. At the moment, a human handler will follow with a joystick, should something go awry. But these machines are actually pretty good at finding their way around. Once one gets to your place, you unlock it with a PIN, grab your food, and send the robot on its way.

Because an operator is following the robot at all times, you might consider the robot to be a fancied-up, slightly more autonomous version of a person pushing a shopping cart. “But that's not the business model that they're going after,” says San Francisco Supervisor Norman Yee, who spearheaded the legislation. “The business model is basically get as many robots out there to do deliveries and somebody in some office will monitor all these robots. So at that point you're inviting potential collisions with people.”

Unlike self-driving cars, or at least self-driving cars working properly, these bots roll on sidewalks, not streets. That gives them the advantage of not dealing with the high-speed chaos of roads, other than crossing intersections, but also means they have to deal with the cluttered chaos of sidewalks. Just think about how difficult it can be for you as a human to walk the city. Now imagine a very early technology trying to do it. (Requests for comment sent to three delivery robot companies—Dispatch, Marble, and Starship—were not immediately returned.)

What happened in that Board of Supervisors meeting was the manifestation of a new kind of anxiety toward the robots roaming among us. Just this last year has seen an explosion in robotics, as the machines escape the lab (thanks in part to cheaper, more powerful sensors) and begin rolling and walking in the real world. They've arrived quickly and with little warning.

And that’s made folks both curious and uneasy. Go to a mall and you may well find a security robot scooting around keeping an eye on things. Robot nurses roam the halls of hospitals. Autonomous drones fill the air. The question is: How are we supposed to interact with these machines? It’s a weird and fundamentally different kind of relationship than you’d form with a human, and not even experts in the field of human-robot interaction are sure how this is going to play out.

The big thing is safety. Machines are stronger than us and generally unfeeling (though that’s changing with robots that have a sense of touch), and can be very dangerous if not handled correctly. Which is what spooked Yee. San Francisco’s sidewalks are bustling with pedestrians and runners and homeless people and dogs and the occasional rat stacked on a cat stacked on a dog. How can the city make sure that roaming delivery robots and citizens get along?

For San Francisco, that means a crackdown. The legislation will require delivery robots to emit a warning noise for pedestrians and observe rights of way. They’ll also need headlights, and each permittee will need to furnish proof of insurance in the forms of general liability, automotive liability, and workers’ comp.

It’s sounds so very un-Silicon Valley. You know, move fast and break things, potentially literally in the case of the delivery robots. But states including Idaho and Virginia have actually welcomed delivery robots, working with one startup to legalize and regulate them early. Though really, San Francisco can better afford to put its foot down here—it’s not like it’s hurting for startups to come in and do business.

Might that seem like San Francisco isn’t as tech-friendly as it may seem? No, says Yee. “If you want to approach delivery, figure out how to do it and be as compatible with our values here,” he says. “Could robots do other things, for instance? Could it be that somebody's accompanying a robot that's picking up used needles in the street?”

If only Silicon Valley wasn't so busy developing parking apps.