Tech giants Google (GOOGL  ) and Oracle (ORCL  ) are facing off at the Supreme Court over the rights to code that Oracle had created, but that Google had used without its permission. The case is a decade old and has been making its way through the court system since with several judgments and subsequent appeals along the way.

The drawn-out legal battle began in 2010 when Oracle sued Google in California for copyright and patent infringement. It was initially ruled that Application Programming Interfaces (APIs) and programming language could not be copyrighted as it would stifle innovation. However, a series of appeals saw various courts finding both in favor of Oracle and Google, with the final judgment before the case reached the Supreme Court being that Google's use of Java API was not fair use.

The hearing began on Wednesday, and it appeared that the court was split. Chief Justice John Roberts was noted as being skeptical of Google's defense, finding its defense that "there was no other way to do it" to be questionable.

"The only reason there is only one way to do it is because some of Oracle's product expression was very successful. There were a lot of ways to do it when they did, and the fact that the programmers liked it and that is what everybody used - it seems a bit much to penalize them for that," Roberts said.

Other justices found similar issues with the argument. Justice Sonia Sotomayor questioned Google as to why it hadn't spent the money to develop its own API much as Apple (AAPL  ) had in developing iOS. Justice Brett Kavanaugh, the most recently appointed Justice whose confirmation remains a point of contention on Capitol Hill, compared Google's use of the API to copying a song's lyrics.

Sotomayor, however, did note the wide-reaching implications of ruling in favor of Oracle.

"Everybody knows that APIs, declaring codes, are not copyrightable. Implementing codes are. So please explain to me why we should now upend what the industry has viewed as the copyrightable elements, and has declared that some are methods of operation, and some are expressions," Sotomayor said.

Justice Steven Breyer also seemed to support Google's argument, comparing the use of API's to the QWERTY keyboard. Allowing the company that developed the keyboard to patent the design would give it a monopoly.

The court case's implications are far-reaching and could upend long-held conventions in the tech industry. The use of APIs by tech companies without licensing them from their creators is standard practice; only small portions of code are typically copied. Most of the code in a given program is created by the developer using the API. A decision in favor of Oracle could allow companies to lock out the use of their APIs unless they license them, which could significantly stifle innovation and ease-of-access to common programming languages that the tech industry has enjoyed for decades.