WHEN THE Supreme Court, in the 2003 case of Grutter v. Bollinger , narrowly upheld the use of racial preferences at the University of Michigan Law School, it emphasized that such preferences were barely tolerable under the Constitution. They could be used only as a last resort, the court ruled, they must not unduly harm non-minorities, and public universities had to start finding ways to phase them out. “We are mindful that ‘[a] core purpose of the 14th Amendment was to do away with all governmentally imposed discrimination based on race,’ ’’ Justice Sandra Day O’Connor wrote for a 5-4...