Forget about Google and Audi and Nissan promising we'll see autonomous cars within the next few years. Elon Musk says he'll roll them out in three months.

The CEO of Tesla Motors says the next big software update for the Model S will roll out in 90 days with an auto-steering function that will make the cars largely autonomous on the highway. The feature will be pretty basic—keeping the car within its lane at an appropriate speed—so it's no big leap. Every Model S built since October has the radar, sonar and other hardware needed to pull this off, and the ability to combine all that data with navigation, GPS, and real-time traffic systems. All that's missing is the software needed to tie it all together.

And possibly permission to actually do it. And that's where things get murky. We asked a few experts if any of this is legal. And the general consensus was ¯\_(ツ)_/¯.

The truth is, none of this is clear, for a few reasons. First, it remains to be seen exactly what Tesla plans to offer. Musk says the feature will be restricted to highway use (follows the trajectory of automakers like Mercedes-Benz and Audi), but did not specify its capabilities. When Tesla first mentioned autonomous features in October, it said "Model S will be able to steer to stay within a lane, change lanes with the simple tap of a turn signal, and manage speed by reading road signs and using active, traffic aware cruise control."

We don't know if that's still the plan, and no one at Tesla returned our call seeking clarification. But on Thursday, Musk said, "there’s certainly an expectation that when autopilot on the Model S is enabled, that you’re paying attention."

Adding to the uncertainty, the rules regulating self-driving cars are a mess. Only California, Nevada, Michigan, Florida, and Washington, D.C. govern how the vehicles can be tested. Those laws largely apply to testing, so the legality of taking a car straight to market there may be flexible: Nevada requires a special license and registration, but that only applies to cars sold in the state. Florida basically legalized it, saying it "does not prohibit or specifically regulate the testing or operation of autonomous technology." In California, the technology can only be tested, and is not allowed for consumer use until further notice. According to Stanford Law School's Center for Internet and Society, 14 more states are working on regulations, and a dozen have voted them down.

This is good news for Tesla. Because this is America, whatever's not illegal is legal. Aside from those states (and Washington DC) that have regulated autonomous vehicles, and New York (which requires drivers keep at least one hand on the wheel at all times) there's no law against Tesla flipping a switch making it possible for the Model S to chauffeur itself down the highway. That leaves 45 states of freedom, and maybe New York, if you're super literal and keep a hand on the wheel without actually doing anything.

So if Tesla goes ahead with its plan, letting its cars drive themselves in some conditions, it wouldn't be breaking the law.

The cars could, however, be kicked off the road if regulators aren't thrilled with the idea of autonomous vehicles roaming the country, says Bryant Walker Smith, an assistant professor at the University of South Carolina School of Law and affiliate scholar at the Center for Internet and Society, who studies self-driving vehicles. There are laws prohibiting reckless driving, for example, and "a state or local law enforcement agency could use these provisions to target" the cars "if they believed the vehicles to be dangerous." That could lead to a revoked registration, or refusal to register cars going forward.

There are no federal regulations in place yet, but based on a 2013 non-binding statement, NHTSA isn't hot on the idea of consumer operation of autonomous vehicles just yet. It "could also attempt to intervene if it has evidence that automated vehicles are not reasonably safe," Smith says.

And what about California, home to Tesla, where the Model S is popular enough to replace the grizzly bear on the state flag? Even with laws governing autonomous tech, it's not clear. It all depends on how the car's capabilities are defined, based on NHTSA standards, which rank automation from Level 0 (you don't even get cruise control) to Level 41 (think Minority Report). Level 2 cars offer some automation, including the combination of adaptive cruise control and lane centering. They're totally legal in California, says Bernard Soriano, deputy director of the state DMV.

But if the software lets the Model S operate like a Level 3 car, letting the human "cede control of all safety-critical functions" to a machine that can, say, change lanes on its own, then it's illegal. Cars with such capabilities, like the Audi A7 I piloted from Silicon Valley to Las Vegas, must be certified as test vehicles before they hit the pavement. You can't sell them to the public.

In those states that haven't yet moved to regulate autonomous cars, Smith says the reaction of regulators likely will depend on how the cars are received by the public, and how well Tesla communicates its intentions. "At this point broad public attitudes will matter as much if not more than particular legal language," he says.

California, for its part, is hardly anti-autonomous driving. It created its rules as a framework for the testing a whole slew of companies were already doing in Silicon Valley, and already is working on rules for allowing Level 3 cars on the market. "We're smack dab in the middle of them now," says Bernard Soriano, deputy director at the state's DMV. He would not offer an ETA, but says "we're close." That process includes the automakers, Soriano says. "We've been working very collaboratively with them and to their credit, they've been very open with us."

Tesla already has gone to legislative war with states that don't let it sell its cars through stores rather than independent dealerships, so don't be surprised if it unleashes its attorneys once again. But so far, it looks like this might be one of those times when seeking forgiveness beats asking for permission.

1Story updated March 20, 2015 at 18:45 EST to include the correct number of levels in NHTSA's autonomous driving scale.