Well, there are two issues it seems to me: Will it be fair? Will it be effective? As to the first, Judge Bolton, who issued the temporary injuction last week, raised several cautions about putting some citizens and legal residents in difficult positions because they either have not been issued or do have to carry with them proof of legal status. This kind of practice will inevitably generate hassles and complaints.
The more important question is: will it be effective? You care counting on cops, who are being very careful NOT to engage in racial profiling randomly having enough encounters that meet the law's conditions in order to perform checks. I think it could be a very round about, very inefficient way to go about enforcing immigration law. It could use up police resources with little to show.