Believe it or not, catalysts were not mandatory in European gasoline-powered cars until 1988. The reason behind that was that the fuel consumption of European cars, noticeably lower than their American counterparts, was considered less of a harm. Then there is the EU (formerly EC) rule of making all decisions unanimously, which with France and Italy on one side and Germany on the other didn't make the process easy. We're seeing a rehash of this in the current discussion on CO2 limits
. Compared to the US Clean Air Act from 1970, it seems Europeans arrived late to the game. Back in 1985, European cars over 2 liters had to use unleaded gasoline and were fitted with catalytic converter. The rule was extended to all gasoline cars in 1993.
[Source: Le Blog Auto