Either marriage is a religious matter (like many argue for Yes on Prop 8) and thus marriage needs to be banned from government and no more legal marriages can take place, regardless of gay or straight (the religious nuts can still have marriages within their church that only their church recognize and have no legal standing)

or

Everybody has to be allowed to get married because it is a state instution, separated from religion, and under which everyone is allowed equal protection.

However, eventually the Courts will overturn this decision, the same that they would if voted to have separated bathrooms for blacks and whites, separate water fountains for gays and straights, etc.