ATF ignoring Federal Courts and moving forward with pistol brace rule?

Just to be clear, I simply think this is just ATF director Detelbach attempting to be a pain in the ass before he resigns and Trump is inaugurated, but the fact that the ATF has the balls to put in writing that they are blatantly ignoring Federal Courts is alarming to say the least. Do I think anything comes of this? No, but just figured I would post it for those interested.