While numerous attempts have been made by local authorities to prosecute these “clean” vandals, the eco-friendly, temporary, and harmless nature of their endeavor has made it difficult and, some may argue, downright silly. Perhaps the most supreme example of irony to date took place in 2007. Following a job pulled by Brazilian artist Alexandre Orion in which he spent two weeks scrubbing soot and grime from a tunnel wall (crafting a mural of skulls in the process), angry local authorities found they couldn’t charge him with anything. Bent on revenge, authorities washed the artwork away. When Orion returned to finish the opposite wall (the mural intended to remind drivers of the damaging effects of car emissions), authorities retaliated by cleaning that side as well. Eventually, authorities made sure every single tunnel in São Paulo was spotless so it wouldn’t happen again.