http://en.wikipedia.org/wiki/Bolling_v._Sharpe
Bolling v. Sharpe, 347 U.S. 497 (1954), is a landmark United States Supreme Court case which deals with civil rights, specifically, segregation in the District of Columbia's public schools. Originally argued on December 1011, 1952, a year before Brown v. Board of Education, 347 U.S. 483 (1954), Bolling was reargued on December 8 and 9, 1953, and was unanimously decided on May 17, 1954, the same day as Brown. The Bolling decision was supplemented in 1955 with the second Brown opinion, which ordered desegregation "with all deliberate speed." Bolling did not address school desegregation in the context of the Fourteenth Amendment's Equal Protection Clause, which applies only to the states, but held that school segregation was unconstitutional under the Due Process Clause of the Fifth Amendment to the United States Constitution. In Bolling, the Court observed that the Fifth Amendment to the United States Constitution lacked an Equal Protection Clause, as in the Fourteenth Amendment to the United States Constitution. The Court held, however, that the concepts of Equal Protection and Due Process are not mutually exclusive.
This says equal protection applies only to states, not D.C. - but that was in implementing a law in D.C., not beyond it.
Instead, this case was decided under the Due Process Clause.
The court, led by newly confirmed Chief Justice Earl Warren decided unanimously in favor of the plaintiffs. In his opinion, he noted that while the 14th Amendment, whose Equal Protection Clause was cited in Brown in order to declare segregation unconstitutional did not apply in the District of Columbia, the Fifth Amendment did apply. Thus setting up the theory of "reverse incorporation." While the 5th Amendment which was applicable in D.C. lacked an equal protection clause, Warren held that
...the concepts of equal protection and due process, both stemming from our American ideal of fairness, are not mutually exclusive.
...discrimination may be so unjustifiable as to be violative of due process.
Is allowing the federal govt to permit law in D.C. that is not granted elsewhere not discrimination against the states themselves?