in England and Wales (probably Scotland and NI as well) it is unlawful in itself and any evidence gathered via this method usually results in the Court case collapsing. Thats not to say the authorities haven’t tried it as recently as the 1990s and 2000s but by then it was very rarely used against drug users or dealers as they were mostly all wise to it as are their lawyers; the main targets tended to be the middle class environmental protestors as those tended to take the moral high ground a bit more.
BTW I am pro-environment myself – I ride my e-bike everywhere rather than own a car, work in a rural area and know loads of small eco-friendly farmers and am always experimenting wiith resilient power systems that can use solar and other renewable sources (much of the info I get from profs in AU) so can understand why the protestors did some of their actions and disagree with the cops tactics; but the eco-warriors were often themselves infiltrated by footy hooligan types (more so than cops!) who just wanted to cause damage and trouble.
