While 'freedom of expression is the lifeblood of democracy', all legal systems now have campaign funding rules and limits and transparency obligations. In the individual sphere it may be that the expression deserves protection irrespective of content, but that does not apply to a campaign. The vast majority if not the totality of the constitutional systems contemplate limits on freedom of expression during an election campaign: for instance, the silence period, cordon sanitaire at polling stations, campaign funding rules and transparency obligations. All campaign restrictions, even those promoting transparency, must be seen firstly as an interference which must be justified, in European systems, according to a test of necessity and proportionality. Regulating the publication of political advertising seems legally possible in the principle for a) Regulation on transparency rather than content, b) regulation on political campaigning, c) Regulation which is either aimed at elections or polls or linked to funding mechanisms or aimed to identify an origin outside the political community. While there are difficult concepts to pin down it is clearly possible to design a scheme for traditional press, broadcasting or poster advertising. But in the digital sphere what is publication and who is the publisher? When is a message “advertising” rather than the individual expression of opinion which “goes viral”?