Twitter is still determined to avoid facilitating mass surveillance by spies and law enforcement. The company has told Dataminr, a firm it partly owns, to stop sharing tweets with the 77 law enforcement fusion centers (that is, data hubs where agencies share info and make connections) in the US. This doesn't prevent police from sifting through Twitter posts, but it certainly makes their work harder. The centers won't have ready access to "billions" of tweets they can pass on to the federal government for spying purposes, according to the ACLU.
This doesn't mean that Dataminr is without government business. Rather, it's emphasizing a "focused" service that delivers breaking news to first responders, including police. The move should help with emergencies while preventing easy user profiling, geospatial analysis (say, where protesters are operating) and other forms of monitoring. Twitter and Dataminr aren't flouting the law, then. They just don't want to contribute to attempts to discourage free speech, whether it's a protest on the street or journalists who challenge political leaders.