Westlaw has a summary, which can be found by searching for the case name "Volkswagen AG v Garcia".  The cause of action was breach of confidence.  The relevant point seems to have been that the researchers did not reverse engineer the software, but obtained it from the internet

 in circumstances which suggested that it had not come from a legitimate source.  This seems to have been taken to mean that it was imparted in circumstances that imported an obligation of confidence, which the publication of the paper would breach.  The risk of theft was a factor justifying the grant of an interim injunction.

The researchers also argued that the publication of the program on the internet meant that it had lost its confidentiality.  Unfortunately, the summary does not tell us why the court rejected this argument, which would on its face seem to be rather strong.

Arvind

From: Andrew Tettenborn <A.M.Tettenborn@swansea.ac.uk>
Date: 28 July 2013 09:25:55 GMT+01:00
To: "obligations@uwo.ca" <obligations@uwo.ca>
Subject: Bentley theft

From the Guardian yesterday:



A British-based computer scientist has been banned from publishing an
academic paper revealing the secret codes used to start luxury cars
including Porsches, Audis, Bentleys and Lamborghinis as it could lead to
the theft of millions of vehicles, a judge has ruled.

<snip>

Has anyone any thoughts as to what the cause of action might have been here?