The U.S. Supreme Court has taken up a major ongoing copyright battle between Google and Oracle over the ownership and use of application programming interfaces (APIs). The APIs allow computer programs to communicate with each other and specify how information is processed and shared.

In the lawsuit, Oracle claims that Google infringed on its copyright by copying the company’s APIs, whereas Google says no one owns the APIs. These APIs were created in 2006 by Sun Microsystems, a copy which Oracle purchased in 2009. Google used the code for the APIs when it created the Android operating system and says APIs are not original expressions that are protected by intellectual property law.

Google is arguing that Oracle is attempting to “control and own standard open source functions that all developers rely on to create software compatible with an established platform, like Java.” Multiple legal scholars have signed amicus briefs agreeing with Google’s position in this battle.

In 2012, Judge William Alsup of the Northern District of California ruled that APIs are not protected under copyright law, knowing that if they had ruled in Oracle’s favor, the company would have been allowed to tie up “a utilitarian and functional set of symbols” that is the basis for many of the programs we use today. Where “there is only one way to declare a given method functionality, [so that] everyone using that function must write that specific line of code in the same way,” coding cannot be copywritten.

Oracle appealed the ruling and the case moved to the U.S. Court of Appeals for the Federal Circuit. In 2013, computer scientists filed an amicus brief, asking the Federal Circuit to uphold Judge Alsup’s ruling. Instead, a year later, the Federal Circuit reversed Alsup’s ruling and said Java APIs are copyrightable.

A few months after the Federal Circuit’s ruling, Google filed a petition with the U.S. Supreme Court, asking them to review the ruling, and another amicus brief was filed by computer scientists, asking the Supreme Court to review the ruling and reverse the ruling, reinstating Alsup’s original ruling; the Supreme Court denied the petition.

This petition was denied in 2015, and the case went to trial in a district court where Google sought the fair use defense for the APIs, and the jury unanimously agreed with Google’s fair use defense in 2016. So, Oracle filed another appeal.

The Federal Circuit Court reversed the jury’s verdict in 2018, after having previously said that this was up to a jury to decide, and said that Google’s use of the APIs was not fair use. Google petitioned the court to rehear the case, and the Federal Circuit denied Google’s petition.

Google filed another petition in January 2019, asking the U.S. Supreme Court to review both of the Federal Circuit’s reversals. Finally, in November the Supreme Court granted Google’s petition. Oral arguments should begin in March, and we may have a decision by June.

The ruling in this case may end up being the deciding factor on exactly how much software can be subject to copyright laws, and it will likely define the way the fair use defense is used in the future.

“This is the copyright case of the century,” said Stanford law professor Mark Lemley, who has represented Google in copyright matters but isn’t speaking for the company in this case. “However it is decided, it has the potential to reshape not only software copyright law but copyright doctrine more generally.”

Having open APIS is what allows programmers to develop software that will work across platforms. It also allows them to update old programs, even if the program was abandoned by its developers. If the Supreme Court sides with Oracle, creating new programs will become much more expensive, people will become less interested in learning new programming languages, people will be trapped with outdated software that requires expensive upgrades, and it will become more difficult to break into the software market.