In Buckley v. American Constitutional Law Foundation, the Court held unconstitutional a Colorado statute that required circulators of initiative petitions to be registered voters. 525 U.S. at 197. Applying a strict scrutiny analysis because petition circulation is "core political speech" for which First Amendment protection is "at its zenith," id. at 186-87, the Court concluded that the registered voter requirement "drastically reduces the number of persons, both volunteer and paid, available to circulate petitions." Id. at 193 (citing Meyer v. Grant, 486 U.S. 414, 423, 100 L. Ed. 2d 425, 108 S. Ct. 1886 (1988)). The state could not justify this burden on political expression with a compelling interest protected by a narrowly tailored restriction, because other reliable safeguards already protected those interests: The State's dominant justification appears to be its strong interest in policing lawbreakers among petition circulators. Colorado seeks to ensure that circulators will be amenable to the Secretary of State's subpoena power, which in this these matters does not extend beyond the State's borders. . . . the interest in reaching law violators, however, is served by the requirement, upheld below, that each circulator submit an affidavit setting out, among several particulars, the "address at which he or she resides, including the street name and number, the city or town, and the county." . . . This attestation, we note, has an immediacy, and corresponding reliability, that a voter's registration may lack. 525 U.S. at 196. Pointing out that no challenge had been made to Colorado's right to require circulators to be state residents, the Court noted that the Tenth Circuit had found that a residency requirement "more precisely achieved the State's subpoena service objective," and concluded: In sum, assuming that a residence requirement would be upheld as a needful integrity-policing measure -- a question we, like the Tenth Circuit, . . . have no occasion to decide because the parties have not placed the matter of residence at issue -- the added registration requirement is not warranted. That requirement cuts down the number of message carriers in the ballot-access area without impelling cause. After Buckley, therefore, the question of the constitutionality of a state residency requirement on petition circulators is left open. Assuming, without deciding, that a state residency requirement would be upheld as a narrowly tailored restriction protecting the state's compelling interest in policing its elections through statewide subpoena power to contact circulators, we do not see how the more restrictive requirement of county residency would survive strict scrutiny. The more local the residency restriction becomes, the smaller the pool of available petition circulators becomes, thus limiting political conversation about proposed changes, but with no corresponding heightened protection of the state's interests in the integrity of its elections. By illustration, the imposition of a county residency requirement would have decreased the pool of available petition circulators from 2,271,290 (the actual number of qualified electors in Arizona in January 1999) to 88,501 (the actual number of qualified electors in Yavapai County in January 1999). Correspondence with Arizona Secretary of State, Sept. 12, 2000. Given the short time frame in which to collect significant numbers of signatures, it is apparent that this restriction would place a heavy burden on political expression regarding referendum issues in our smaller counties.