Tesla Inc. (TSLA) shares have been riding high lately thanks to enthusiasm around the company's self-driving technology. But a new legislative proposal could complicate that narrative in a hurry.

The "Stay in Your Lane Act" Takes Aim

Sen. Ed Markey (D-Mass.) just introduced a bill with one of those congressional names that tells you exactly what it's about: the "Stay in Your Lane Act." The legislation would force automakers developing Level 2 and higher autonomous systems to face restrictions based on road types, weather conditions, and geographic locations, according to The Verge.

Here's where it gets interesting for Tesla. The company currently lets drivers use Full Self-Driving across the country without geographic restrictions. Markey's bill would establish what it calls "operational design domains"—basically, a set of conditions that must be met before autonomous features can legally operate.

"Self-driving cars aren't a danger of the distant future — they are a pressing safety threat today," Markey told The Verge. "Too often, certain car companies are rolling out autonomous driving features without responsible limitations on when and whether they can't be used, leading to avoidable injuries and deaths."

Notice that phrase "certain car companies"? The bill makes the target even clearer by holding up General Motors Co (GM) and Ford Motor Co (F) as positive examples—companies that already limit where their Level 2 systems can operate. When a bill praises your competitors for doing something you're not doing, it's probably about you.

Under Markey's proposal, the National Highway Traffic Safety Administration (NHTSA) would have the power to fine companies that fail to comply with the operational design domains. This isn't Markey's first rodeo with Tesla either. Back in October, he was among several senators calling for an investigation into FSD over safety concerns, particularly vehicles failing to detect railroad crossings.

The Political Landscape Gets Complicated

Now, Republicans control Congress, which typically makes life harder for Democratic bills. But autonomous vehicles have become one of those rare issues that bothers politicians on both sides of the aisle.

Sen. Josh Hawley (R-Mo.) announced plans last September for his own autonomous vehicle legislation. Hawley called self-driving cars "terrible for working people" and declared that "only humans should drive cars and trucks." His proposed "Autonomous Vehicle Safety Act" focused more on fully autonomous vehicles that could replace cab drivers and truckers, rather than driver-assistance features like FSD, but it shows the bipartisan skepticism at play.

Then there's President Donald Trump, who said in October 2024: "Do you like autonomous? Does anybody like an autonomous vehicle? Know what that is? Right? When you see a car driving along? Some people do, I don't know. A little concerning to me, but the autonomous vehicles we're going to stop from operating on American roads."

Of course, Trump's relationship with Tesla CEO Elon Musk has evolved considerably since then. The political support and friendship between the two may have softened the president's stance. But Trump also appointed Jonathan Morrison, a known Tesla critic, to lead the NHTSA. So the regulatory picture remains murky at best.

Why This Matters Now

The timing of Markey's bill is particularly noteworthy. It arrives just after a California ruling determined that Tesla's marketing for FSD and Autopilot was deceptive. The company now faces a potential 30-day sales and production ban in the state.

For Musk, the stakes couldn't be higher. He's projected that Tesla could hit a $20 trillion valuation if the company's plans for FSD, robotaxis, and the Optimus humanoid robot pan out as envisioned. Regulatory restrictions on where and how FSD can operate would throw a serious wrench into that vision.

The Democratic-led bill faces real obstacles in a Republican-controlled Congress. But given the bipartisan unease about autonomous vehicles and recent safety incidents, it might find more support than typical party-line legislation. Whether it passes or not, the "Stay in Your Lane Act" signals that Tesla's unrestricted approach to rolling out self-driving technology is drawing serious regulatory scrutiny from Washington.