Law professor Dan Solove’s article, Fourth Amendment Pragmatism, generated a good amount of discussion among privacy advocates and the legal community. In one discussion over on Scott Greenfield’s Simple Justice blog, both Dan and law professor/former DOJ prosecutor Orin Kerr participated. Unlike some of us who think that Fourth Amendment case law has eroded Fourth Amendment protections and is an incoherent mess, Orin generally seems more positive about the state of things. When I bitched complained lamented that as a member of the public, I should be able to know whether I have a reasonable expectation of privacy or not, Orin responded by referring me, in part, to his article on the four models of Fourth Amendment protection and by writing:
As a citizen, you know when you have a reasonable expectation of privacy when the courts tell you — they announce a rule, and that rule sticks, to cover those facts. At that point there is no fluctuation or uncertainty: The rule is the rule.
After checking to make sure that there was no smiley emoticon at the end of his comment, I thought it quite striking how what seems so acceptable to him is so unacceptable to me. Given how fact- or situation-specific most decisions are and given that I don’t think we should need to wait for a court decision to find out if we had a reasonable expectation of privacy or not in a situation, I found Orin’s answer totally unsatisfactory.
Although many Fourth Amendment discussions are framed in terms of criminal activity and defendant’s rights, the Fourth Amendment applies to all of us and not just those engaging in criminal activity. How can we make informed decisions about whether to use a cell phone, whether to use cloud services, or whether to share information with an insurance carrier if we do not know the extent to which such activities would require a warrant to compel disclosure? In my opinion, the four-model approach that Orin sees as working well does not work at all – much less, well – if it means that our reasonable expectation of privacy depends on what jurists are considering the case in what jurisdiction and which of the four models they choose — at their discretion — to apply.
Today I read the new Third Circuit decision with a mixture of appreciation and frustration. While the court said that courts may require a warrant, which is certainly better than saying that they cannot require a warrant, saying what courts may do moves us no closer to a bright line by which citizens can be assured that their location data will not be searched without a warrant or demonstration of “probable cause.”
And so, with tongue firmly planted in cheek, I propose a seven-model approach to Fourth Amendment protection. The approach uses a different model for each day of the week so that citizens need only consider the day of the week to know whether they have a reasonable expectation of privacy or not. Don’t expect to see the article in any law journals, though. While psychologists have it drilled into our heads to avoid footnoting like the plague, it seems that many legal scholars cannot compose a single sentence that is footnote-free. Indeed, finding sufficient footnotes might be a bigger challenge than lack of actual legal scholarship in my endeavor. 
Of course, Congress could actually remedy the situation by enacting legislation that would make the lines clearer. Don’t citizens and law enforcement both deserve to — and need to — know where the line is in what law enforcement may obtain without a warrant?