If the Supreme Court specifically states it's the legislature's job to change the law, and the legislature expressly fails to do so, and if the Supreme Court also is not changing the law (and it may not), then the old law is still binding, and the ONLY CONCLUSION one can legitimately draw is that Romney acted inappropriately -- enforcing an OPINION that wasn't legally binding on him or the state.
What's more, even if the court came out and said that he MUST allow gay marriage (which it did not), without the approval of the legislature, if he is sworn to uphold both the federal and state constitutions (which he was), he MUST refuse.
Another person who hasn't READ THE DECISION!!! Taking a quote out of context and distorting what they decided.
Here's what they decided: 1) The existing law, as commonly interpreted, violated the civil rights of homosexuals.
2) Overturning existing law (MA 207) would be too disruptive a remedy for (1), because it would wipe out legal marriage in MA.
3) They would therefore finesse the law by changing the operative common law interpretation of "civil marriage" and leave the existing code in place. If the legislature disagreed with the interpretation, they had 180 days to act to clarify the definition in the civil code.
The old law IS still in place, and Romney WAS bound by it. But the MEANING of marriage as used by the law had changed. The existing law said he had to issue licenses to all "parties" who applied and were legally entitled. Those not entitled were A) blood relations; B) those already married; C) minors without permission; and D) people coming from out of state to marry, where it would violate their home state's laws to do so (written to originally keep interracial couples from entering the state to marry).
The judiciary is not authorized to change the meaning of a law, because that would be writing a new law.
If the existing law was sufficient and needn't be changed in order to accommodate "civil unions," then there would be no REASON to direct the legislature to change it. Because the legislature decided not to change it, the law STILL DID NOT accommodate civil unions.
As EV said, the governor's duty is to the Constitution, and whenever an opinion of the court violates the principle terms of that Constitution, he is bound by his oath to defy it. Checks and balances are in place to prevent abuse of this executive discretion.