Jonathan Adler at Volokh posts on the federal judge's order blocking the administration's guidance to schools on bathrooms, finding that they didn't comply with the Administrative Procedure Act beloved of all bureaucrats. Adler doesn't note that similar problems arose with the administration's effort to change the rules on undocumented immigrants. The bottom line is the executive branch didn't go through a rule-making procedure, allowing the public to comment, before issuing the document. To be cynical, the executive thought if the document wasn't labeled a "regulation", rule-making wasn't required.
So the Obama administration has suffered two defeats this year on issues dear to liberal hearts. There's some small consolation in this idea: if the Trump administration (:-( should try similar tactics in order to undo or change liberal policies, liberals would have a stronger case to force the Trumpites into the long rule-making process.
Just as a matter of history, I suspect these two episodes are just another step in the long history of changing administrative procedure into formal regulations. The lawyers have to make work for themselves.