An application programming interface is the glue that holds complex software systems together. Until 2014, it was widely assumed that no one could use copyright law to restrict APIs' use—a view that promoted software interoperability.

Then, in 2014, a court known as the Federal Circuit Appeals Court issued a bombshell ruling taking the opposite view. Oracle had sued Google, arguing that Google had violated Oracle's copyright by re-implementing APIs from the Java programming language. The case has been working its way through the courts ever since, with the Federal Circuit issuing a second controversial ruling in 2018. On Thursday, Google asked the Supreme Court to overturn the Federal Circuit's controversial ruling.

"The Federal Circuit's approach will upend the longstanding expectation of software developers that they are free to use existing software interfaces to build new computer programs," Google wrote in its Thursday petition to the Supreme Court.