In the Mexican state of Zacatecas, the electoral authority is testing a new technique for controlling the amounts of spending and enforcing spending limits - they purchased all the television and radio time parties are allocated to use and prohibit parties from purchasing any media time by other means, be it with their state-provided or private finance. This also allows for easy monitoring of infractions of the prohibition, as well as ensuring that the media doesn’t give discounts to its preferred parties (although I do not know if this occurs in Mexico or Zacatecas).
The report (spanish) at UNAM’s La Jornada also discusses the electoral authorities rules against “dirty” campaigning and allegations by the PAN that the resources (employees) of the Zacateca’s state are being used to help the PRD’s campaign. With regard to the former, the electoral authority already removed two media “spots” in which the PRD accused the PAN of wanting to raise the prices of certain goods in the “basic basket,” which earned the PRD a fine of about US$3600.