The New Jersey Supreme Court (State of New Jersey v. Shirley Reid (A-105-06) [PDF]) has issued an important decision on Internet users’ right to privacy. The case involves a dispute about whether an ISP violated a user’s privacy rights by turning over subscriber information (name, address, billing details) associated with a particular IP address. It ends up that the subpoena served on the ISP was invalid for a variety of reasons. As the user had a ‘reasonable expectation of privacy’ in her Internet activities and identifying information, and because the subpoena served on the ISP was invalid, the New Jersey court determined that the ISP should not have turned over the personal data.

The important aspect of this case in the evolving understanding of privacy on the Internet is the court’s recognition that we must look at privacy from the broad perspective of what can actually be discovered about people online. In this way, the ruling has significant strengths and weaknesses from a privacy perspective. On the one hand, the court finds that there is, today, an expectation of privacy in IP addresses because they are currently hard to link to personal identity. There have been lots of disputes in the US and the EU about whether IP addresses are ‘personally identifying information.’ (“PII” in the jargon of privacy.) This court takes a pragmatic view of this question and finds that IP addresses should be considered private for now, but that this may change. The court finds:

the reasonableness of the privacy interest may change as technology evolves. A reasonable expectation of privacy is required to establish a protected privacy interest… Internet users today enjoy relatively complete IP address anonymity when surfing the Web. Given the current state of technology, the dynamic, temporarily assigned, numerical IP address cannot be matched to an individual user without the help of an ISP. Therefore, we accept as reasonable the expectation that one’s identity will not be discovered through a string of numbers left behind on a website.

The availability of IP Address Locator Websites has not altered that expectation because they reveal the name and address of service providers but not individual users. Should that reality change over time, the reasonableness of the expectation of privacy in Internet subscriber information might change as well. For example, if one day new software allowed individuals to type IP addresses into a “reverse directory” and identify the name of a user—as is possible with reverse telephone directories—today’s ruling might need to be reexamined.

Others have written about the legal details of this case and have suggested that it is a big win for privacy. Given the reliance on the shifting state of identity technology, I’m a little less sanguine.

This case is yet another reason why I believe (as I’ve explained elsewhere [PDF]) that meaningful privacy on the Web requires rules that govern how personal information is used, not just what can be collected. Under the court’s reasoning, as our lives become more and more transparent, that would justify increasing harmful use of personal data. While it’s pretty hard to control how exposed we are all become, we still can limit how powerful institutions (governments, etc.) use personal data about us.