COLD, HARD FACTS OF LIFE POLICE CHIEF-AUTHOR WALKS A PRAGMATIC BEAT.(BOOKS)

Byline: CHRISTOPHER D. RINGWALD

He infiltrates a band of Jewish terrorists, spends 20 years as a detective in New York, flies helicopters, become a police chief on Cape Cod and publishes four books before confronting this question: Do citizens have an inalienable right to dash into the woods?

One soft night in June, Richard Rosenthal, Wellfleet's burly, bespectacled chief, sat at the head table in a packed library meeting room and considered the proposition. He faced a mixed crowd of tie-dyed teenagers, well-dressed and fit retirees, local residents -- both blue-collar and professional workers, and off-duty cops. Many were still roiled by a racially tinged incident in February. That day, by police accounts, an officer spotted Mamadou Sow, a young black man, walking along a bike trail in an area where …