Article II, section 5(c) of the California Constitution provides (emphasis added),

The Legislature shall provide for partisan elections for presidential candidates, and political party and party central committees, including an open presidential primary whereby the candidates on the ballot are those found by the Secretary of State to be recognized candidates throughout the nation or throughout California for the office of President of the United States, and those whose names are placed on the ballot by petition, but excluding any candidate who has withdrawn by filing an affidavit of noncandidacy.

As the court's unanimous decision (in Peterson v. Padilla) put it,

Elections Code sections 6883 and 6884 purport to make the appearance of a "recognized" candidate for president on a primary ballot contingent on whether the candidate has made the disclosures specified by the Act. This additional requirement, however, is in conflict with the Constitution's specification of an inclusive open presidential primary ballot. The Legislature may well be correct that a presidential candidate's income tax returns could provide California voters with important information. But article II, section 5(c) embeds in the state Constitution the principle that, ultimately, it is the voters who must decide whether the refusal of a "recognized candidate[] throughout the nation or throughout California for the office of President of the United States" to make such information available to the public will have consequences at the ballot box.

The court acknowledged that the "recognized candidates" requirement might require some definition of who is "recognized," and that perhaps perhaps "the Legislature might properly claim some role in defining when someone is" so recognized. But the requirement here, the court explained, had nothing do with providing any such definition:

[U]nder any reasonable interpretation of the "recognized" language within article II, section 5(c), a candidate's failure to disclose tax returns to the Secretary of State would not establish that the candidate is not "recognized … throughout the nation or throughout California" as a candidate "for the office of President of the United States." The word "recognized" is susceptible to somewhat different meanings. (Compare, e.g., Black's Law Dict. (4th ed. 1968) p. 1436, col. 2 [defining "recognized" as "[a]ctual and publicly known"] with Random House Dict. of the English Language (1973) p. 1199, col. 3 [defining "recognize" as, among other things, "to acknowledge or treat as valid"].) The repeated use of the word "throughout" within article II, section 5(c) suggests that the "recognized" language is concerned (although perhaps not exclusively) with a candidacy's prominence or pervasiveness. (See Webster's 3d New Internat. Dict. (1971) p. 2385, col. 1 [defining "throughout" as "in … every part of"].) If this meaning applies, it seems plain that whether a candidate has disclosed tax returns to the Secretary of State cannot, by itself, be determinative of whether the candidate is "recognized." Such disclosure has, at most, a highly attenuated relationship to public awareness of a candidacy throughout the nation or California—or, for that matter, to whether someone is an "[a]ctual" candidate for the presidency. (Black's Law Dict., at p. 1436, col. 2.) The disjunctive "throughout the nation or throughout California" language in article II, section 5(c) also suggests that nondisclosure of tax returns under the Act could not supply a basis for keeping a presidential candidate off the primary ballot even if the "recognized" phrasing were to be construed as being to some extent concerned with a candidacy's validity. For even in that case, a failure to comply with the Act's tax return disclosure requirement would establish only that someone is not "recognized," i.e., not regarded as valid, as a presidential candidate in or by California. It would not mean that the candidate is not "recognized … throughout the nation," because a failure to satisfy this requirement would not make a candidacy invalid throughout the nation.

The court had no occasion to determine whether the provision also violated the U.S. Constitution (see the federal district court decision in Griffin v. Padilla).