If your google adsense account is diasabled, you can try to enable again. Many times it happens that you had not done any illegal activity and even then your account is disabled. For example your competitors may click on your ads to make your account activity suspicious.

If your google account is disabled then you must read this article. The main reason is that publishers are doing against the google terms and conditions and want to earn more money by using the illegal means. Sometimes your competitors may also do this for you.