Under EU rules, internet service providers may not block, slow down, alter, restrict, interfere with, degrade or discriminate when providing an internet access service. In its report, BEREC specifically references the fact that these rules also apply to advertising: 

"By way of example, ISPs should not block, slow down, alter, restrict, interfere with, degrade or discriminate advertising when providing an IAS, unless the conditions of the exceptions a), b) or c) are met in a specific case," the report states. 

The exceptions the report refers to relate to: ISPs being subject to union or national legislation measures; preserving the integrity and security of the network and end-user equipment; and preventing network congestion. 

Commenting on the report, Allan Sørensen, policy committee chairman of IAB (Interactive Advertising Bureau) Europe, said: 

“Hopefully the timing of the guidance, coming as it does when network-level ad blocking remains limited to isolated cases in sub-regions of the EU, will nip the problem in the bud.  

"Consumers have the right not to receive online advertising if they choose not to, and to compensate publishers and providers of other online services in some other way.  But the imposition of network-level blocking would have nefarious medium- to long-term consequences for European media and Europe’s digital economy.”