The Supreme Court will hear arguments on Monday in a case that could lead to sweeping changes to America’s controversial computer hacking laws — and affecting how millions use their computers and access online services.

The Computer Fraud and Abuse Act was signed into federal law in 1986 and predates the modern internet as we know it, but governs to this day what constitutes hacking — or “unauthorized” access to a computer or network. The controversial law was designed to prosecute hackers, but has been dubbed as the “worst law” in the technology law books by critics who say it’s outdated and vague language fails to protect good-faith hackers from finding and disclosing security vulnerabilities.

At the center of the case is Nathan Van Buren, a former police sergeant in Georgia. Van Buren used his access to a police license plate database to search for an acquaintance in exchange for cash. Van Buren was caught, and prosecuted on two counts: accepting a kickback for accessing the police database, and violating the CFAA. The first conviction was overturned, but the CFAA conviction was upheld.

Van Buren may have been allowed to access the database by way of his police work, but whether he exceeded his access remains the key legal question.

Orin Kerr, a law professor at the University of California, Berkeley, said Van Buren vs. United States was an “ideal case” for the Supreme Court to take up. “The question couldn’t be presented more cleanly,” he argued in a blog post in April.

The Supreme Court will try to clarify the decades-old law by deciding what the law means by “unauthorized” access. But that’s not a simple answer in itself.

“The Supreme Court’s opinion in this case could decide whether millions of ordinary Americans are committing a federal crime whenever they engage in computer activities that, while common, don’t comport with an online service or employer’s terms of use,” said Riana Pfefferkorn, associate director of surveillance and cybersecurity at Stanford University’s law school. (Pfefferkorn’s colleague Jeff Fisher is representing Van Buren at the Supreme Court.)

How the Supreme Court will determine what…