In one of its central descriptive senses, ‘discrimination’ means the differential treatment of persons, however justifiable or unjustifiable the treatment may be. In a distinct but still primarily descriptive sense, it means the disadvantageous (or, less commonly, the advantageous) treatment of some persons relative to others. This sense is not purely descriptive in that an evaluative judgment is involved in determining what counts as a disadvantage. But the sense is descriptive insofar as no evaluative judgment is made regarding the justifiability of the disadvantageous treatment.
In addition to its descriptive senses, there are two normative senses of ‘discrimination’. In the first, it means any differential treatment of the individual that is morally objectionable. In the second sense, ‘discrimination’ means the wrongful denial or abridgement of the civil rights of some persons in a context where others enjoy their full set of rights. The two normative senses are distinct because there can be morally objectionable forms of differential treatment that do not involve the wrongful denial or abridgement of civil rights. If I treat one waiter rudely and another nicely, because one is a New York Yankees fan and the other is a Boston Red Sox fan, then I have acted in a morally objectionable way but have not violated anyone's civil rights.
Discrimination that does deny civil rights is a double wrong against its victims. The denial of civil rights is by itself a wrong, whether or not others have such rights. When others do have such rights, the denial of civil rights to persons who are entitled to them involves the additional wrong of unjustified differential treatment. On the other hand, if everyone is denied his civil rights, then the idea of discrimination would be misapplied to the situation. A despot who oppresses everyone equally is not guilty of discrimination in any of its senses. In contrast, discrimination is a kind of wrong that is found in systems that are liberal democratic but imperfectly so: it is the characteristic injustice of liberal democracy.
The first civil rights law, enacted in 1866, embodied the idea of discrimination as wrongful denial of civil rights to some while others enjoyed their full set of rights. It declared that “all persons” in the United States were to have “the same right…to make and enforce contracts…and to the full and equal benefit of all laws…as is enjoyed by white citizens.” (42 U.S.C.A. 1981). The premise was that whites enjoyed a fully adequate scheme of civil rights and that everyone else who was entitled to citizenship was to be legally guaranteed that same set of rights.
It is a notable feature of civil rights law that its prohibitions do not protect only citizens. Any person within a given jurisdiction, citizen or not, can claim the protection of the law, at least within certain limits. Thus, noncitizens are protected by fair housing and equal employment statutes, among other antidiscrimination laws. Noncitizens can also claim the legal protections of due process if charged with a crime. Even illegal aliens have limited due process rights if they are within the legal jurisdiction of the country. On the other hand, noncitizens cannot claim under U.S. law that the denial of political rights amounts to wrongful discrimination. Perhaps the citizen-noncitizen distinction tracks something like the distinction between civil and political rights that proved to be unsustainable when applied to citizens.
The application of much of civil rights law to noncitizens indicates that many of the rights in question are deeper than simply the rights that constitute citizenship. They are genuine human rights to which every person is entitled, whether she is in a location where she has a right to citizenship or not. And civil rights issues are, for that reason, regarded as broader in scope than issues regarding the treatment of citizens.