Scalia cites exclusion of free blacks

The SCOTUS decision re: Arizona's immigration restriction law is generating a lot of interest. Here's my two bits to the discussion: 1) Can anyone explain why, supposedly, the Dept. of Justice never mentioned "racial profiling" when presenting its case before the Court as to why the "show your papers" provision should be struck down. Because they didn't, the Court didn't take that consideration into account in reaching their decision. If anyone can explain how "determining someone might be here illegally" is done in any way other than visual observation of the features of a suspect, along the lines of what those here illegally are stereotyped to look like. They won't be questioning the status of Irish or German "visitors" who overstayed their visas. 2) Antonin Scalia, in his exuberance to prove the historical precedent for the state's prerogative to police their own borders cites this: "...in the first 100 years of the Republic, the States enacted numerous laws restricting the immigration of certain classes of aliens, including convicted criminals, indigents, persons with contagious diseases, and (in Southern States) freed blacks." (p. 4 of his dissent; see http://www.supremecourt.gov/ and click on "6/25/12 - Arizona v. United States" at right column to get a pdf of the ruling) One of our proud moments that we'll certainly want to cite as precedent for similar actions to be allowed today. What the Be-hell? Not to mention the dubious nature of his claims--non-slave states were probably more likely to prohibit the entry of blacks than were Southern states the entry of free blacks.