Hi.

Before attending law school, law advisor typically earn a bachelor's degree in pre-law or a comparable discipline. After graduating, potential legal advisoaa are required to take and pass the law School Admission Test (LSAT) and enroll in a law school that is accredited by the American Bar Association (ABA). And basically There is no fixed criterion to be a Legal Advisor, but some of the general requirements to be a Legal Advisor are 

Be a firm or company (individuals are generally not eligible);

Have practiced corporate finance;

Have acted on Relevant Transactions during the study of corporate finance.

Hope it helps.