Back in the 20s and 30s in the US, the mob ran roughshod over the land. The only way devised to corral them-- because of massive corruption on local, state, and federal levels-- was to invoke tax laws. It worked. It got Capone, and a bunch of the mob.
What really ended that era of gangsterism? Prohibition was repealed. We didn't see the return of that type of gangsterism until the war on drugs.
The war on drugs doesn't stop or restrict drug use it creates wealthy powerful gangsters.
This type of privacy violating law needs to go. If you are suspected of a crime the cops should need to get a warrant to have the banks show them your transactions. Monitoring your finances without a warrant is not fundamentally different than tapping your phone or planting a GPS on your car without one.