Citing its potential to have a detrimental effect on housing markets and economy as a whole. a Minnesota-based Realtor association has taken a public stance against a proposal to amend the state's constitution to recognize only marriages of opposite-sex couples as valid. Same-sex marriage is already illegal in Minnesota under a 1997 law. But a constitutional amendment would make it harder to overturn that law, because another statewide vote making gay marriage legal would be required. Currently, the law could be overturned by the state Legislature or by a judicial ruling, as was done in Iowa in 2009, for example. The Minneapolis Area Association of Realtors, which has nearly 7,000 members, said the proposed constitutional amendment would have a "negative impact on equal access to...