According to Right to Life of Michigan, drivers would be able to purchase the specialty plates to support the pro-life cause.
Lawmakers have previously tried to bring up similar legislation, but it has failed. According to mlive.com:
About half the U.S. has "Right to Life" specialty plates, but their roll-out has been contentious. Groups in several states have mounted legal challenges on First Amendment grounds, some successfully, some not. The Supreme Court has let stand state rulings barring production of the plates.
Most recently, in November, a North Carolina judge blocked production of the plates until a legal battle was resolved. The American Civil Liberties Union argued production of the plates constituted "viewpoint discrimination" because there was no corresponding pro-choice alternative.