The Law:

Felons in prison cannot vote. Once an individual has completed his or her sentence, the right to vote is automatically restored. During the 2000 election, Massachusetts voters passed an initiative to create a constitutional amendment outlawing currently incarcerated inmates from exercising their right to vote. There are no current estimates available of the number of individuals disfranchised in Massachusetts since the law was changed.

Getting Your Vote Back:

http://www.sentencingproject.org/pdfs/rights-restoration/Massachusetts.pdf