You do get a challenge because of the general rule that laws should be written in as technologically neutral a fashion as possible to prevent them from having to be revised or revisited every year or two.
The way that technology changes does lead to challenges. In terms of a good formula, criminal procedure is not my specialization, but I will endorse the lawful access provisions that David Fraser has put forward as a way of providing for proper procedure for obtaining warrants to access subscriber information.