In US district court in San Francisco, California, a gay couple and a lesbian are suing to overturn the voter passed constitutional amendment which bans same sex marriage in California, The basic issue they present is that the right to marry is a constitutional right and that they are discriminated against by not being allowed to marry the person of their choice. They are asking the court to overturn the CA ban on gay marriage.
The challenge in federal court is risky. If the court rules against them it will affirm the right of a state to ban gay marriage. Whatever the decision the case will be appealed to the US supreme court. If the court rules on the issue it will settle the issue of of whether there is a federal right to same sex marriage.
This issue last came to the supreme court in 1972 in Baker v Nelson in which the Minnesota supreme court ruled the state could ban gay marriage. The gay couple had cited the US. Supreme Court decision in Loving v. Virginia which overturned laws against interracial marriage. The MN court ruled that in a constitutional sense and in commonsense there is a clear distinction between a marriage restriction based on race and one based on the fundamental difference in sex.
The US supreme court dismissed the appeal or want of a federal question, meaning there was no US constitutional right to gay marriage.That has been the controlling case in federal law for 38 years leaving each state to choose whether to ban gay marriage. At this time 5 states allow gay marriage, 45 do not.
In Baker v Nelson the supreme court dismissed an appeal and did not directly rule on the issue.The risk to gay supporters is that if they lose this in the supreme court there can not be another federal challenge to bans on gay marriage. The supreme court is hesitant to overturn previous rulings so the chances are that they will rule against gay marriage being a federal constitutional right.