Unlike in India, law is not studied formally at the undergraduate level in the US. Students can take a loose set of courses dubbed "pre-law" to help prepare for law school after finishing their Bachelors but it is not a pre-requisite and is not offered as a major at Harvard ( http://webdocs.registrar.fas.harvard.edu/ugrad_handbook/current/ )
Gates went to Harvard for Computer Science and pre-law and had he finished, he would have most probably majored in Comp Sci. Poorly thought-out question.
