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In early 2012, Google(s goog) swept Oracle in what the presiding judge described as the “World Series” of intellectual property trials, leading the court to declare that Oracle(s orcl) could not assert copyright over Java APIs, aka application programming interfaces.

Now, a rematch is underway in Washington, D.C. where an appeals court is indicating that it could rule in Oracle’s favor and, in doing so, pour legal cement on a basic building block of web architecture.

If you’re unfamiliar with the case, the key issue is whether or not APIs — structural pieces of software that let different programs talk to each other — qualify for copyright protection. In the original trial, US District Judge William Alsup, who is well-versed in California tech issues, said that APIs are not eligible for protection on the grounds that they are a basic idea, not a form of creative expression.

During a Washington hearing on Wednesday, however, Bloomberg reports that Circuit Judge Kathleen O’Malley stated that, even though Java is free for anyone to use, that status does not negate the ability to obtain copyright protection.

This will please Oracle, whose lawyer told the court that Google “took the most important, the most appealing” part of Oracle’s Java language to build its Android operating system.

Google countered that it only used the basic command structure, on which it laid 15 million lines of original code.

If Oracle succeeds in the appeal, it will obtain a level of control over software construction that would be akin to a construction firm saying it had exclusive rights to a Phillips head screwdriver.

The D.C. appeals court, which has been criticized in the past as a “rogue” forum for intellectual property law, has yet to rule. If it does declare that Oracle owns the APIs, there is still the possibility that the case could be remanded for a jury to find if Google’s use of them amounted to a permitted “fair use.”

A fair use ruling could ensure a key software tool remains open to all but would be less effective than maintaining the original decision that Java API’s are not copyrightable in the first place.