Lawsuit: Whom to sue? Sue for what?

I read AILF's message for lawsuit and here is my brief and shallow analysis

(1) To sue USCIS?
It seems the only reason to sue USCIS is its rejection of "other workers" petition in June.
This is because the rejection is against June Bulletin. For July rejection of all employment-based petition, USCIS has the support of DOS's Revised July bulletin. In this
sense, if you still file your case now in order to sue USCIS, to my understanding, it is useless but paying lawyers the legal fee.

(2) To sue DOS?
For revision of July Bullitin? Do they have the legal right to do so? I didn't find any information in AILF;s message about this.