The Euro 2 emissions standards were put in place for passenger cars in January of 1993. Russia adopted these standards in the fall of 2005, and the limits will soon have a very real impact on vehicles entering - or trying to enter - central Moscow. According to a Google-translated page from Auto Lenta-RU
, cars that don't meet the Euro II standards will not be allowed into central Moscow starting on the first of September this year. The reason is to improve the environment in the city - no "congestion charge" wording here. New cars that are made in Russia shouldn't have a problem meeting this level, but early editions of the Zhiguli don't. Since early April, trucks that don't meet the standard were banned from the inner city.
[Source: Auto Lenta-RU
, h/t to TheRookie