Chris Geidner of Metro Weekly has the deets:
[N]o still viable decision by this Court has deemed a valid foreign marriage to be "repugnant," despite being void or punishable as a misdemeanor or more serious crime were it performed in Maryland. The present case will be treated no differently. A valid out-of-state same-sex marriage should be treated by Maryland courts as worthy of divorce, according to the applicable statutes, reported cases, and court rules of this State.
More importantly, even if a referendum is qualified this June (and passed this November) to invalidated Maryland's recently passed marriage equality law, Maryland residents can still go get married in any of the 6 states (and Washington, D.C.) that allow same-sex marriage and their marriage will be valid or legal in Maryland as well. It would take a state constitutional amendment to overturn this decision by Maryland's highest court.
This was already believed to be the law in the state of Maryland (like in Rhode Island) due to opinions issued by the relevant Attorneys-General of those states, but a ruling by the state supreme court settles the issue in Maryland and an executive order issued by the Governor of Rhode Island strengthens (but does not completely settle) the legal situation in that jurisdiction.