[jotux]

Here's the law for CA: http://leginfo.legislature.ca.gov/faces/codes_displaySection....

"Shall be provided with respect to any voter, subject to the provisions of Sections 2166, 2166.5, 2166.7, and 2188, to any candidate for federal, state, or local office, to any committee for or against any initiative or referendum measure for which legal publication is made, and to any person for election, scholarly, journalistic, or political purposes, or for governmental purposes, as determined by the Secretary of State."

Looks like ultimately it's whatever the Secretary of State allows.

[DrScump]

The difference is that counties charge everybody but party central committees for voter data or extracts. (Or such was the case when I did voter data wrangling 15 years ago).