In its decision of 19 October 2016, the Court of Justice of the European Union ("CJEU") clarified the concept of personal data. The Court held that an IP address can be qualified as personal data, even if the processor could only identify the actual user through information on the IP address held by an Internet Service Provider ("ISP").
Personal data, which are pivotal in the application of Data Protection Directive 95/46/EC ("the Directive"), are broadly defined as any information relating directly or indirectly to an identifiable natural person.
The case that led to the submission of questions to the CJEU for a preliminary ruling is about the German politician Mr Patrick Breyer (Pirate Party) who visited several websites operated by German Federal institutions. The website operator (the Federal German Government) stored information on the IP addresses of its visitors. Breyer argued that his IP address qualifies as personal data and that therefore, pursuant to the Directive, the website operator would have to obtain Breyer's consent to store his IP address. The Federal German Government was of the opinion that the IP address did not qualify as personal data, so the issue ended up before the Bundesgerichtshof (Federal Court of Justice, Germany) and this Court submitted the preliminary questions to the CJEU.
The CJEU began by reaffirming its previous ruling in the Scarlet Extended case in which it essentially held that the IP addresses of internet users were protected personal data because they allow users to be precisely identified.1] However, that finding related to the specific situation in which the collection and identification of the IP addresses of internet users are carried out by ISPs.
What makes this case different to the Scarlet Extended case is that it is not the ISP but rather the website operator who is collecting the IP addresses of website visitors. The Federal German Government does not have direct access to the additional data that are necessary for it to identify the user behind the IP address because that information is held by the ISP. Furthermore, the IP address from Breyer was a "dynamic IP address" that changes every time the user connects to a network, making identification of the user virtually impossible without additional information from the ISP.
The CJEU notes that it is common ground that a dynamic IP address as such does not qualify as personal data, since such an address does not directly reveal the identity of the natural person who owns the computer from which a website was accessed. To identify a natural person behind a dynamic IP address, additional data is needed, and such data is held by the ISP and not by the website operator.
The CJEU continued by investigating whether a dynamic IP address can qualify as personal data if there is indirect access to such information held by the ISP. The CJEU noted that if the information needed from the ISP is legally or practically unobtainable, the risk of user identification by the website operator appears in reality to be insignificant. However, the CJEU held that dynamic IP addresses are personal data if the website operator has "the legal means which enable it to identify the data subject with additional data which the internet service provider has about that person."
As for the specific case at hand, the CJEU considered that for cyberattacks, website operators do have access to legal channels that enable them to obtain the information from the ISP to identify the data subjects behind the dynamic IP addresses. This consideration is subject to verification to be performed by the German Federal Court. If the German Federal Court finds this consideration valid, then Breyer's dynamic IP address will qualify as personal data.
In this ruling, the CJEU introduces a further “subjective” or “relative” criterion to define personal data. Whether information is personal data depends on the capability of the processor to identify the natural person behind the data. Although this criterion stems directly from the wording of the Directive/GDPR, one can easily see that it can lead to qualification issues.
The case (C-582/14) can be found here.
ECLI:EU:C:2016:779 paragraph 33 (Breyer) referencing to ECLI:EU:C:2011:771 paragraph 51 (Scarlet Extended).
 We note that the European Data Protection Authorities ("DPAs") broadened the scope even further by concluding that every static IP address is, or should be treated as, personal data, since in theory it would be possible to gather enough information about the browsing history of an individual so that he or she could be identified.
 ECLI:EU:C:2016:779 paragraph 46 (Breyer)