Yeah, I doubt that is the case. But if it is the case, as long as he is not talking policy with them, it’s perfectly legal.
Even talking policy is legal. I have witnessed ex-presidents and presidential candidates swarming around the world meeting with foreign leaders to discuss policy. Hell Obama literally trailed Trump around the world to do so. CANDIDATE Obama met with the Iraqi government in September of 2008 and told them he would be elected in 6 weeks so they shouldn’t sign the Status of Forces agreement with Bush because he would be changing it.