Wrongfully Demoted. Any retaliation?

[top1percent]

Let me apologize for the long story. I have been working with a very successful company for three years now. During this three years, I have had several promotions and pay increases. As of 10 months ago, I was the Assistant to the V.P. of the company, as well as, the Insurance Contracts Manager. While working at this position the President of the company approached me to take a position as his assistant. This would be a position that I had no formal training to do, but could be a real learing and growing experience for me. However, after careful consideration I declined the position. I was very happy in my current position and decided this would not be the best move for me to make at the time. The next month after his offer came my annual review. In this review I was given a glowing report and recommendation for a substantial pay increase. Needless to say, I was very pleased. Then, about a month later the President of the company approached me again and strongly urged me to take the position as his assistant. He told me that I was the only person he felt could do the job. Then, he finally asked me what it would take for me to accept. We agreed on an additional pay increase and I accepted the position. Since accepting this position, I have never received any written job description, nor have I received any training for this position. It seems that I was set up to fail. Now 10 months later, he's decided that I can't handle the position and he is demoting me to another position that I have no formal training. And he's decreased may pay by 25%. This is much lower than my payrate at my previous position that I had received glowing reviews. This payrate is equal to what I received when I started with the company 3 years ago. Is this legal? Is there any sort of retalition? He's also told me that he didn't think I would succeed at my new position, and he would understand If I wanted to quit. There's plenty more to the story, but this should give you a good idea of what has happened. Is there anything I can do?
Thanks for your help!