"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
When slavery was outlawed by the US Constitution does that mean existing slaves must remain with their masters??? Using the pro gay marriage logic, the answer would be YES.
The AG disagrees with your assessment on ex post facto grounds. The status of those marriages will definitely be battled in the courts.