"The officer turned on his heel and ran off before she could injure him. Only later did she find out that "Reclaim the Streets" was holding a demonstration farther down the road." (227)
Reclaim The Streets is a collective with a shared ideal of community ownership of public spaces. Participants describe it as a resistance movement against the dominance of corporate forces in globalization and cars as the dominant mode of transportation.
Often times, non-violent protests would be planned, such as invading major roads, highways, and freeways to stage a party. Although this obstructs the regular users of this space, those part of the collective reason it is in fact "the vehicle traffic, not pedestrians, who are causing the obstruction." The idea of these protests is to state that the roads should be open public spaces.
However, one outlying issue is that these demonstartions did take a turn for the worst, some times becoming violent riots.
Salander more than likely encounter the police officer during May of 1998 near the Reclaim The Streets demonstration. This can be inferred because the only notable demonstrations held in Stockholm, Sweden, during the writers lifetime was in May 1998, September 1999, and May 2003.