The verb enfranchise is used when a group of people are given voting rights or freedoms they didn't have before. Many people under the age of 18 would like lawmakers to enfranchise their peer group so they can vote.
Enfranchise traces back to the Old French word enfranchiss, a combination of en-, meaning "make, put in," and enfranchir, meaning "to set or make free." In the 1680s, enfranchise came to mean "to admit to membership in a state," something that usually came with the right to vote. You may know the word disenfranchised, an adjective that describes people who lack rights or liberties. To enfranchise is to give or restore rights to the disenfranchised.