I thought Posse Comitatus does not apply to the national guard, in fact the National Guard has excersised police powers before.
Well what they think they can do and what they can actually do are two very different things.
Do not forget that the UN called the USA "mean" for attempting to deny any kind of migration.
Human rights will be another angle.
Please understand that their goal is not to win in any court. Their goal is to tie up the courts with suits. Cost the taxpayers money to the point that it is too expensive to fight. You know, kind of like capitol punishment is today!!!!!