Aircraft on approach to CRW received TCAS RA from a helicopter operating from a downtown location; reporter suggesting this ATC authorized procedure be amended to preclude future TCAS events.

Narrative

On a visual daylight approach to Runway 5 in CRW; backed up by the ILS; I was the pilot flying. We received a traffic advisory between 4 and 3 miles from touchdown. TCAS showed traffic 700-800 FT below us. Visual contact with traffic was not established. At about 3 miles out TCAS issued a resolution advisory to monitor vertical speed; and then do not descend. The descent was stopped and within 3-5 seconds the RA was resolved. Traffic displayed on TCAS at our 6 o'clock and not a factor. Impact on glide path/airspeed was minimal; and a normal landing was executed. After the event CRW Tower informed us that helicopters are authorized to takeoff directly underneath the approach to Runway 5 without first establishing contact with CRW Tower. The helicopter in this event was required to submit a report. I would have to speculate as to the reason this occurred. We were cleared to land. Suggestion; require radio contact with CRW Tower before helicopters can takeoff from any nearby heliports; or establish a departure procedure for the heliports that requires a turn away from the approach path before a climb is authorized. There is an agreement between CRW ATC and the copters that they may lift off from down town CRW and climb to 700 FT before talking to ATC. Personally I think this is to small a margin since downtown is right underneath the glideslope to 5. This copter was unaware of our presence