There's nothing that the general did that was a violation of any sort. He was well within his duties to discuss issues of common concern between the two countries. I will say it again, that what this came down to is a matter of trust. The President was glad that he was out there, conducting his job, preparing for his job.
Going back and forth with his counterparts throughout the world. What came down to, plain and simple, was him misleading the Vice President and others, and not having a firm grasp on his recollection of that. So the question wasn't, did he do anything improper or illegal? It's a question of, could he be trusted further?
And that trust, or the erosion of that trust, was frankly the issue.