It is likely that most Missourians believe marriage is intended for couples consisting of a man and a woman. That has been the religious and cultural model until recent years, when same-sex couples have sought to have their unions legally sanctioned.

A lopsided 128-20 procedural vote this week in the Missouri House suggests fairly widespread support for an amendment to the state constitution that would ban same-sex marriages -- even though state law already prohibits same-sex unions.

But as much as many Missourians would like to prevent same-sex marriages in this state, there are major issues raised by the proposed constitutional amendment. And those issues may be difficult to resolve.

This is not just a Missouri issue, of course. Efforts are being made to add an amendment to the U.S. Constitution that also would bar same-sex marriages. Many states are struggling with legislative attempts to take a stand on this issue. And some states face rulings from their highest courts saying same-sex unions must be allowed.

One issue raised by the proposed constitutional amendment in Missouri is the distinction between civil and religious marriage ceremonies. Proponents say only civil marriages would have legal standing. Under the proposal, churches would not be prevented from allowing religious ceremonies for same-sex marriages -- but those unions would not be recognized by the state.

Much of the push for banning same-sex marriages is based on religious beliefs. Indeed, church-going Missourians place a higher premium on their religious marriage vows than they do on the marriage license they were required to obtain at some county courthouse.

Moreover, very few denominations would allow a marriage ceremony without a marriage license. The recent Unitarian ceremony in suburban St. Louis for two women was a rare exception. Thus, the proposed amendment's ban on civil same-sex unions while allowing religious ceremonies seems to add confusion rather than making a clear stand.

The other big issue is the full faith and credit clause of the U.S. Constitution, which requires states to recognize other states' laws. It would take a legal battle to clarify how Missouri's proposed ban would affect same-sex couples who are married elsewhere and become Missouri residents.

Whether Missouri voters will actually support a constitutional amendment remains to be seen.