Facebook CEO Mark Zuckerberg has been ordered to testify in the intellectual property dispute between virtual reality company Oculus VR and ZeniMax Media, due to claims of his “unique knowledge” in the matter gained through Facebook’s $2 billion acquisition of Oculus last year.

The ongoing dispute over intellectual property was filed by ZeniMax against Oculus, back in May 2014. ZeniMax Media alleges Oculus commercially exploited intellectual property relating to VR technology that was shared under a non-disclosure agreement, which enabled Oculus to improve upon its own virtual reality headset.

Oculus has defended its position against the claims as merely an attempt by ZeniMax to cash in on the $2 billion Facebook purchase of Oculus.

Facebook’s legal team suggests ZeniMax’s request for testimony by Zuckerberg was not proper or relevant, stating in a Facebook filing documented by PCWorld, “This is clearly improper under the apex doctrine, which requires a party to demonstrate that a high-ranking corporate executive has unique, relevant personal knowledge before attempting to take their deposition.”

Much of the lawsuit revolves around the early days when John Carmack before he joined Oculus in August 2013, had previously worked for id Software, a ZeniMax subsidiary, first began to allegedly collaborate with Oculus founder Palmer Luckey on a very early prototype of the Oculus Rift—which Carmack demonstrated at E3 2012 running a version of Doom 3 specifically modified for virtual reality.

During this period, ZeniMax argues, Carmack allegedly used VR technology belonging to ZeniMax, and without it, the Oculus Rift headset would not have been possible of becoming a viable product, while also adding that ZeniMax received no compensation for the use of its technology in developing the Rift.

Clearly, this legal battle has a long way to go until it’s finally resolved. Stay tuned for more on the latest updates on this story, as it continues to develop.