A gang led by a criminal-turned math teacher was responsible for one of France’s biggest tax-frauds between 2008 and 2009. The group exploited a weakness in the EU’s carbon-trading scheme: they bought carbon credits that were sold without VAT in most European countries, and sold them with VAT in France, without paying the difference to the state. They made close to € 400 million, which they laundered through a network of shell companies, luxury goods and real estate.