Appellants, faculty members of the State University of New York and a nonfaculty employee, brought this action for declaratory and injunctive relief, claiming that New Yorks teacher loyalty laws and regulations are unconstitutional. Their continued employment had been terminated or was threatened when each appellant faculty member refused to comply with a requirement of the university trustees that he certify that he was not a Communist and that if he had ever been one he had so advised the university president; and the nonfaculty employee refused to state under oath whether he had advocated or been a member of a group which advocated forceful overthrow of the government. Under 3021 of New Yorks Education Law "treasonable or seditious" utterances or acts are grounds for dismissal from the public school system, as well as under 105, subd. 3, of the Civil Service Law. Other provisions of 105 of the Civil Service Law disqualify from the civil service or employment in the educational system any person advocating or involved with the distribution of written material which advocates the forceful overthrow of the government. Section 3021 does not define "treasonable or seditious." Section 105, subd. 3, provides that "treasonable word or act" shall mean "treason" as defined in the Penal Law and "seditious word or act" shall mean "criminal anarchy" as therein defined. Section 3022 (the Feinberg Law) of the Education Law requires the State Board of Regents to issue regulations for the disqualification or removal on loyalty grounds of faculty or other personnel in the state educational system, to make a list of "subversive" organizations, and to provide that membership therein constitutes prima facie evidence of disqualification for employment. The Board listed the National and State Communist Parties as "subversive organizations" under the law, but shortly before the trial of this case the university trustees certificate requirement was rescinded and it was announced that no person would be ineligible for employment "solely" because he refused to sign the [385 U.S. 589, 590] certificate, and that 3021 and 3022 of the Education Law and 105 of the Civil Service Law constituted part of the employment contract. A three-judge District Court sustained the constitutionality of these provisions against appellants challenges of vagueness and overbreadth and dismissed the complaint. Held:

1. Adler v. Board of Education, 342 U.S. 485, in which this Court upheld some aspects of the New York teacher loyalty plan before its extension to state institutions of higher learning, is not controlling, the vagueness issue presented here involving 3021 and 105 not having been decided in Adler, and the validity of the subversive organization membership provision of 3022 having been upheld for reasons subsequently rejected by this Court. Pp. 593-595.

2. The rescission of the certificate requirement does not moot this case, as the substance of the statutory and regulatory complex challenged by appellants remains. P. 596.

3. Section 3021 of the Education Law and 105, subds. 1(a), 1 (b), and 3, of the Civil Service Law as implemented by the machinery created pursuant to 3022 of the Education Law, are unconstitutionally vague, since no teacher can know from 3021 of the Education Law and 105, subd. 3, of the Civil Service Law what constitutes the boundary between "seditious" and nonseditious utterances and acts, and the other provisions may well prohibit the employment of one who advocates doctrine abstractly without any attempt to incite others to action, and may be construed to cover mere expression of belief. Pp. 597-604.

(a) These provisions, which have not been interpreted by the New York courts, can have a stifling effect on the "free play of the spirit which all teachers ought especially to cultivate and practice" (Wi