What this article wants you to believe:

Police are actively using flock to identify people traveling over state borders to buy marijuana and search their cars.

What actually happened:

Police used flock to locate someone with an active warrant for their arrest related to domestic violence. They noticed a pattern of crossing state lines at certain times, and used that to nab him. It turns out it was to buy marijuana and his car reeked of it, so he was charged with that, too.