A council press release said Ušakovs was sending a letter of complaint to VVC director Maris Baltiņš disputing the agency's right to impose penalties over Facebook content as it is a US-registered company not registered with Latvia's Public Utilities Commission as an internet service or electronic communications provider.
Furthermore, users of Facebook must agree in advance to its terms and conditions of use which set rules to create your own personal profile, express your thoughts and share them with other people.
As users control who can see posts and who cannot, Facebook cannot be regarded as a blanket communication tool aimed at the whole of Latvian society, the mayor argued in his defense. Basically, it's a one-on-one deal to which people subscribe or unsubscribe voluntarily, not a mass communication tool.
In his letter Ušakovs also draws attention to alleged procedural violations in the decision to impose a sanction such as inconsistencies in the dates quoted by VVC to justify its ruling.
"Riga City Council points out that the decision taken by the VVC is considered unjustified, and the application of the law and procedures inappropriate, with the result that it should be annulled," the release concludes.
As previously reported by LSM, the mayor fell foul of a recent ruling by the "language police".
The VVC maintains that it is not against the use of foreign languages including Russian and English in the council's communications - but insists any such communication must first be made available in Latvian.
However the battle between Ušakovs and Baltiņš seems to be increasingly personal with the latter spikily admonishing the mayor for using "third-rate wit" in his reaction to VVC's ruling.
Latvian is the only official state language in Latvia and while around a quarter of Latvia's population is ethnically Russian, the proportion of ethnic Russians is considerably higher in the capital, Riga at around 38% compared to 46% Latvians.
A 2013 referendum on making Russian an official state language was comfortably defeated.