The Canadian military has quietly started deploying counter-drone systems around its major ports and air bases as it grapples with both the technology and the legalities of shooting down uncrewed aerial vehicles (UAVs), CBC News has learned. 

The idea is to prevent the kind of grey-zone warfare incidents that have recently paralyzed parts of northern Europe, and to avert the kinds of surprise attacks which have characterized the war between Russia and Ukraine. 

The effort has largely gone on behind the scenes and is still a work in progress in some cases, mostly because of rapid advances in drone tactics and technology.