In all the arguments and debates on both sides of this issue, I never once heard anyone bring up the question of why and how a marriage performed in one state is (or up until now, always has been) automatically considered valid in every other state. It's just been taken for granted, assumed as a given, without anyone ever wondering why. There IS a reason: The US Constitution, Article IV, Section 1. "Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State." Marriage is a "public Act and Record," and as long as the legal definition of marriage was the same in all 50 States (man/woman), every State was required by the US Constitution to give "Full Faith and Credit" to a marriage performed in any other State. On June 16, 2008, California's definition of marriage was changed to "any two persons" by a 4/3 Court decision. Since then, only Massachusetts and Connecticut were Constitutionally required to give Full Faith and Credit to a California marriage. The other 47 were not required to do so. Any State except Massachusetts or Connecticut could have refused to honor any California marriage (including a man/woman marriage). Now that California voters have passed Proposition 8, the man/woman definition will be written into the State Constitution. All other states must now give Full Faith and Credit to every California marriage (except the ones that were performed between June 16 and November 4). Since Massachusetts and Connecticut define marriage as "any two persons," they must also give Full Faith and Credit to California marriages because a man and a woman are "any two persons." This is how Proposition 8 has "protected" marriage - by ensuring that all Californians married here must be considered married anywhere.