Hello dear Grapeviners, please help me out! TLDR-Shifted to the client side from Agency, non competition clause came in picture.

Hello everyone, please help me with this dicey situation. My friend A recently joined one of the clients which were linked with his previous employer,The Agency. Though he didn't directly switch from the agency to the client, but had 2-3 months experience at a whole new Startup which wasn't related to the agency, but the issue is that the same agency is still working with the said Client. Though it wasn't mentioned at the time of joining in the agency, that a non competition clause is there, but the policies were revised, and honestly no one heed attention to it. So as stated, no one could switch to the client side within a year after leaving the agency. He worked so hard in the agency, that the client themselves approached him to join them when they got to hear about his resignation. Could you all please help a fellow here?? Would the agency take any action against it? There is no action taken by the agency right now, but the news of him joining the client definitely wreaks havoc in the agency, especially between the incompetent people working there. Please give suggestions regarding how to defend the job, and also if any of you faced any such things in the past! It's a request from the bottom of my heart. Thanks!