The specific case before them involved an anonymous woman who called 911 to report a driver who forced her off the road. She gave the driver's license plate number and the make and model of his car as well as the location of the incident in question. Police officers later found him, pulled him over, smelled marijuana, and searched his car. They found 30 pounds of weed and subsequently arrested the driver. The driver later challenged the constitutionality of the arrest, claiming that a tip from an anonymous source was unreliable and therefore failed to meet the criteria of reasonable suspicion, which would have justified the stop and search. Five of the nine justices disagreed with him." The ruling itself (PDF).
Justice Sonia Sotomayor reacted sharply in disagreeing with the decision in a 58 page dissent. 'For members of historically marginalized groups, which rely on the federal courts to protect their constitutional rights, the decision can hardly bolster hope for a vision of democracy (PDF) that preserves for all the right to participate meaningfully and equally in self-government.' The decision was the latest step in a legal and political battle over whether state colleges can use race and gender as a factor in choosing what students to admit. Michigan has said minority enrollment at its flagship university, the University of Michigan, has not gone down since the measure was passed. Civil rights groups dispute those figures and say other states have seen fewer African-American and Hispanic students attending highly competitive schools, especially in graduate level fields like law, medicine, and science."