Phil Weiser is Attorney General of Colorado and a candidate for Governor of Colorado. He has filed a LOT of lawsuits against President Trump. I'm sure he really believes in quite a few of them but -- even though he's my friend -- I also think a lot of this is to boost name ID and donations and support from the Democratic base against a better-known (though maybe not yet better-funded) opponent, Sen Michael "cheaper than Sominex" Bennet.
Colorado's AG has filed about 30 lawsuits against Trump administration - Axios Denver
Colorado attorney general lawsuits against Trump tracker - The Colorado Sun
Newish one: Colorado jumps onto lawsuit against USDA over demand for personal information of SNAP recipients
Of course he is: Defending Colorado - Colorado Attorney General | Colorado Attorney General
Pushback: Mesa County to countersue Polis, Weiser over ICE traffic stop
Will he sue over this too? I actually think the federal case is fairly weak but I'm definitely not an expert: Thousands lose in-state tuition breaks under Trump's immigration crackdown | AP News