In the same way reading communications can be perfectly legal and is often helpful in establishing conspiracy cases. Accepting that Governments can legally intercept communications with some form of due process shouldn't be viewed as going after "pre-crime". It has always been the case before now that legal interception powers also enable illegal Government (or indeed non-state) snooping, that should be dealt with by robust interventions by an independent judiciary.
* Road Traffic Law is one of the relatively few criminal areas that is UK wide