To remand something is to send it back from whence it came. The only Federal court that can remand a case back to a state court is SCOTUS if a case progresses first through the state court system and then goes to SCOTUS. Judge Hillman in Worcester can't tell the SJC or the Worcester County Superior Court what to do with this case.
That being said, I don't buy
@Boston4567 's argument that there's literally nothing a Federal lawsuit can accomplish. Federal courts normally use state law when making decisions. The plaintiffs' argument in this case is that the AG overstepped her constitutional and statutory bounds. A Federal judge can examine Mass state precedent and law and make that determination when applying Massachusetts law. Put it this way, this case is past the motion to dismiss stage. If there was nothing for Judge Hillman to rule on, nothing for him to decide, the case wouldn't have survived the motion to dismiss stage of litigation as that's more or less the question Federal judges ask when examining a motion to dismiss: is there a plausible question of law or fact? If you really want to learn more (I don't suggest normal people doing this as its very boring), look up
Twombley and
Iqbal.
Another thing to keep in mind is that the case hasn't been removed from Federal to state court. If what
@Boston4567 is true and there was literally no issue of Federal law to deal with or a diversity issue (as in interstate diversity), then the case would have to have been removed from Federal court to the state court. Removal is a formal process that defendants can motion for if there's no Federal question or the parties aren't from different states. That hasn't happened here and we're beyond the stage where the AG would've moved for removal - meaning there's some question of Federal law here that isn't best answered in state court.
There's a number of advantages to getting a case into Federal court. Normally, its faster than progressing through state courts. I don't know what's up with the Mass state cases in Mass Superior Court so I don't know if that advantage is manifesting here. Federal case law has precedent value in Federal court (here, 1st Circuit) and is only of persuasive value in state court. If you're going to make an extremely complex legal argument, you're probably better off doing that in Federal court as Federal judges see more complex cases more often.