I am curious too.  I have heard it has something to do with the fact that the in order to apply for DACA they had to provide personal information with the idea that the government would not use to harm them and the government has reneged on this.  Something like that...not sure they have an argument though.  (Note that I am pro-DACA and would love to see congress give those already protected under DACA full path to citizenship).  We shall see how it all shakes out...