P brought this action in United States District Court on behalf of herself, her child, and others similarly situated to enjoin the 'discriminatory application' of Art. 602 of the Texas Penal Code. P alleges that one Richard D. (D) is the father of her child, that D has refused to provide support for the child, and that although P made application to the local district attorney for enforcement of Art. 602 against D., the district attorney refused to take action for the express reason that, in his view, the fathers of illegitimate children were not within the scope of Art. 602. A three-judge court was convened pursuant to 28 U.S.C. 2281, but that court dismissed the action for want of standing. Held: Although appellant has an interest in her child's support, application of Art. 602 would not result in support but only in the father's incarceration, and a private citizen lacks a judicially cognizable interest in the prosecution or nonprosecution of another.