As so often is the case, stating that principle doesn’t ease the challenge of line-drawing. In many cases, it would not be overly onerous for authorities to obtain a warrant to search through phone contents. They could still trump Fourth Amendment protections when facing severe, exigent circumstances, such as the threat of immediate harm, and they could take reasonable measures to ensure that phone data are not erased or altered while a warrant is pending. The court, though, may want to allow room for police to cite situations where they are entitled to more leeway.
But the justices should not swallow California’s argument whole. New, disruptive technology sometimes demands novel applications of the Constitution’s protections. Orin Kerr, a law professor who blogs on The Washington Post’s Volokh Conspiracy, compares the explosion and accessibility of digital information in the 21st century with the establishment of automobile use as a virtual necessity of life in the 20th: The justices had to specify novel rules for the new personal domain of the passenger car then; they must sort out how the Fourth Amendment applies to digital information now.