Google's Eric Schmidt, Larry Page, and Sergey Brin pose with one of the company's self-driving cars. Note the cumbersome sensor unit on the roof. Mass-produced self-driving cars will have sensors integrated into the car's body. Photo credit: Google.

Google (NASDAQ:GOOGL) has wowed the world with its self-driving cars, and the search-engine giant would love to commercialize the technology. It's not alone: Automakers from General Motors (NYSE:GM) to Tesla Motors (NASDAQ:TSLA) have recently confirmed that they have systems that will drive your car for you -- at least sometimes -- under development.

That "sometimes" qualifier is important, though. While a car that can drive itself represents advanced technology, a lot of that technology is already mainstream. Many luxury cars, and even some mass-market models like Ford's (NYSE:F) Fusion, are already available with the special radar sensors and cameras that will be key parts of the self-driving cars of the future.

Technology, it turns out, probably isn't the biggest thing holding back self-driving cars. Instead, as Fool contributor John Rosevear explains in this video, it's the legal framework around self-driving cars -- or rather, the lack of one -- that has made automakers very cautious about rushing this new technology to market.