Here's an odd thing I've found as a foreigner living in Washington, D.C.: The longer I'm here the more alien I feel. Assimilation isn't working for me. With the passage of time, the four-way stop (for instance) seems more perplexing, not less. Last week's Supreme Court decisions focused my attention on another exceptionally American weirdness: race-based affirmative action.

You may have to be American to regard this idea as anything other than nuts. A kind of nationally willed suspension of disbelief is required to think about it without laughing. How did a nation dedicated to equality before the law ever decide that the remedy for racism and its legacy is institutionalized race-based preference? It would be hard to come up with a better way to entrench resentment of minorities among poor whites or to cast suspicion on the achievements of successful black and Hispanics.

Judging from its jurisprudence on the matter, the Supreme Court finds the subject as confusing as I do. Explicit quotas are illegal, but racial discrimination is permissible as part of a holistic approach (meaning one that hides the discrimination from view). Could you run that by me again?

I understand and admire the desire to correct and atone for the original sin and consequences of slavery. In the 1960s, when racial integration and equal opportunity were starting from zero, and emergency action to achieve speedy redress was necessary, the deliberate injustice of race-based preferences made some sense. But 50 years later? With Barack Obama in the White House?

Last year Richard Sander and Stuart Taylor published "Mismatch: How Affirmative Action Hurts Students It's Intended to Help, and Why Universities Won't Admit It." It's a fine book, and the evidence gathered under the first part of the subtitle is convincing. As they wrote in a piece for the Atlantic:

The single biggest problem in this system -- a problem documented by a vast and growing array of research -- is the tendency of large preferences to boomerang and harm their intended beneficiaries. Large preferences often place students in environments where they can neither learn nor compete effectively -- even though these same students would thrive had they gone to less competitive but still quite good schools.

I was even more intrigued by the second part -- about the reluctance of the universities and respectable opinion in general to recognize the defects of the policy. It's a subject that cannot be discussed, least of all in the precincts of American institutions dedicated to fearless free inquiry. The authors explain in the Atlantic piece:

Simply acknowledging the fact that large preferences exist can trigger accusations that one is insulting or stigmatizing minority groups; suggesting that these preferences have counterproductive effects can lead to the immediate inference that one wants to eliminate or cut back efforts to help minority students.

What form should that help take, then, if not race-based admissions preferences? First of all, of course, stamp on discrimination against minorities where it exists. Second, spare no effort to raise the pre-college educational attainment of all economically disadvantaged students, regardless of color. When you're sure that preferences will actually help the intended beneficiaries, make them class-based not race-based.

As for other American oddities: Don't even get me started on plea bargains.

(Clive Crook is a columnist and editorial writer for Bloomberg View. Follow him on Twitter.)