A320 pilot reported while on final approach being advised of helicopter traffic resulting in the pilot receiving an TA and reducing their descent rate to avoid the traffic.

Narrative

We were vectored for the RNAV Z XXL into ZZZ. Somewhere between ZZZZZ and ZZZZZ1 ATC informed us of law enforcement helicopter traffic to our south and below our altitude and were told they would stay clear of us.During our descent on profile we received a TCAS Traffic Advisory for the helicopter.On TCAS they showed 300 feet below our altitude. I reduced our descent rate to insure we don't get any closer. At no point did myself or the FO see the helicopter traffic as they were below us.Shortly after adjusting our descent rate the TA subsided and I was able to continue on the descent for a normal and landing.At no point during the approach did I feel unsafe however it was uncomfortable not having the helicopter traffic in sight with a 300 foot separation. Especially since [we] were descending on profile for landing.Once on the ground I called ZZZ tower to discuss the event. The controller I spoke to was very professional and showed a willingness to help. The controller took down the flight information and mine and said he would look at the flight track and voice transmission.A couple of hours later the controller contacted me.He explained that the helicopter traffic was law enforcement and was in pursuit along the freeway. He mentioned that this occurrence is not standard however does not happen often. The controller added that the helicopter had us in sight and later turned south during the pursuit.I completely understand that this may not happen very often; but believe it should not happen at all especially in light of the events in DCA.Law enforcement pursuits have the potential of being anything but controlled flights and the aircraft flying the pursuit may have to maneuver erratically. It is my belief that in instances like the one I described; where helicopter or aircraft traffic is maneuvering at low altitudes near the approach end or departure end of a busy airports more care should be taken.