The Court of Appeal upheld a decision from the UK High Court in July 2015, which found Siemens did not infringe the patent held by Wobben Properties for technology developed for rival manufacturer Enercon.
Dong Energy, special development companies for the Westermost Rough and Gunfleet Sands projects — suspected of using the patented technology — and vessels specialist A2Sea were also named in the court case.
The High Court found Enercon's case was invalid, indicating there was "prior art" that predated the Wobben patent.
Enercon appealed the 2015 decision, arguing the High Court judge "made a series of fundamental errors in assessing the evidence of the expert witnesses", according to the Court of Appeal ruling.
However, three court of appeal judges rejected the appeal, confirming the lower court judge "made no error of principle in his reasoning".
In January 2016, Spanish turbine manufacturer Gamesa won an appeal against a 2013 Barcelona commercial court verdict over alleged illicit use of storm control technology patented by Wobben.