Indiana University has joined a campaign fighting a proposed state constitutional amendment that would ban same-sex marriages.

The university announced Monday it was joining Freedom Indiana, a bipartisan coalition that includes Eli Lilly and Co., Cummins Inc. and the Indianapolis Chamber of Commerce.

IU President Michael McRobbie said the amendment would turn some prospective employees away from Indiana and increase the state's challenges to remaining economically competitive.

The General Assembly overwhelmingly approved the proposed ban in 2011, but the current Legislature would need to approve it again before it would go to voters in a statewide referendum. Indiana law already bars same-sex marriage, but backers of the constitutional ban say it would provide an impediment to potential court decisions that would overturn the state law.

Thirty states have constitutional amendments banning legal recognition of same-sex marriage and five others, including Indiana, ban it by law.