Google was dealt a blow Friday in a multibillion-dollar lawsuit alleging its Android operating system infringes on intellectual property owned by Oracle.

A federal appeals court granted Oracle's appeal in the case, ruling that programming interfaces in Oracle's Java technology can be protected under U.S. copyright law.

Oracle says Google relied on the interfaces to create its popular Android mobile operating system, so the appeals court ruling means Oracle can now continue to pursue its legal case against Google.

"We are extremely pleased that the Federal Circuit denied Google's attempt to drastically limit copyright protection for computer code," Oracle said in a statement.

The federal appeals court referred the case back to the U.S. District Court in San Francisco, where the two sides will have to return to do battle.

Oracle sued Google four years ago, saying its Android operating system infringes on patents and copyrights related to Oracle's Java technology.

Specifically, Oracle says Google copied the "structure, sequence and organization" of some key Java APIs (application programming interfaces) in developing Android.

The jury agreed with Oracle that Google used its APIs in Android, but they were deadlocked on whether it was protected by "fair use" law, which allows copying in some limited circumstances.

The appeals court has now referred the case back to the District Court in San Francisco, where a different jury will have to decide whether Google's use of the APIs was protected.

In a complex case, Google had argued that the APIs should not be copyrightable at all under U.S. law. It argued that they're needed by developers to write interoperable software programs.

A District Court judge agreed with Google, and Oracle appealed the decision to the U.S. Court of Appeals for the Federal Circuit. It's that court that ruled in Oracle's favor on Friday.

The case could have wider implications for the software industry. Some developers argued that making the APIs subject to copyright law would limit their ability to build compatible programs and would stifle innovation. Many big software vendors disagreed and said APIs are creative works that are worthy of protection.

The appeals court came down on the side of the vendors.

"We're disappointed by this ruling, which sets a damaging precedent for computer science and software development, and are considering our options," Google said in a statement.

Oracle said it was "extremely pleased" with the ruling.

"The Federal Circuit's opinion is a win for Oracle and the entire software industry that relies on copyright protection to fuel innovation and ensure that developers are rewarded for their breakthroughs," Oracle said in its statement.

"We are confident that the district court will appropriately apply the fair use doctrine on remand, which is not intended to protect naked commercial exploitation of copyrighted material," Oracle said.

James Niccolai covers data centers and general technology news for IDG News Service. Follow James on Twitter at @jniccolai. James's e-mail address is james_niccolai@idg.com