Wu, who has refused to leave the job, had fired the three men but the board then re-appointed them.
Control of Arm China remains with Wu and the company has now sued the three men.
Additionally, two minority shareholders have sued Arm China seeking to overturn the decision to dismiss Wu.
The lawsuits could take years to resolve which might delay the Nvidia takeover.
The Beijing competition authorities also have to approve the the transaction.
The situation arose because Arm sold a majority stake in Arm China to Chinese investors.
Under China law, control of a company requires possession of the company stamp and registration documents and Wu has held onto them.