Second Circuit Grants Trump's Stay in discovery in Pair of DACA Suits - Page 2

Google says: A (writ of) mandamus is an order from a court to an inferior government official ordering the government official to properly fulfill their official duties or correct an abuse of discretion.

Sounds to me like the judge is saying he believes Trump didn't do due dilligence or had an arbitrary reason for rescinding DACA.

I read a few days ago, although I forgot where, but an article said that if Trump's reason for cancelling DACA was solely to push congress to pass legislation, it would be considered an arbitrary and capricious decision and the judge would tell him to undo it (the DACA recision).