Fire him. That is my solution. Or take away AutoCAD all together. If he is an engineer, should he be doing his own CAD? Hire a CAD slave and take that out of his pay. (lol) But, seriously, I would make sure that someone is keeping a file on him, if he goes out of his way to change the standards, make it as difficult as possible to change things. If his job is harder and harder each and every day, maybe he will bend a little. Other than that, I personally would start tracking his standards deviations, and on a weekly basis, and in a very direct and professional meeting, sit down and explain WHY the standards are the way they are. (If he can't adopt them, perhaps he would be better off starting his own company?) I would also have documentation as to what was said, when, his replies, and what purpose he hopes to achieve. MAYBE some of the things he does, perhaps they are done like that for a reason... (stupidity? ignorance of autocad?? he didn't know how to do it any other way, therefore he may do it the only way he knows)
Here is a thought: what about reverse psychology? You know, like a 4 year old ... lol good luck