On French roads only with an alcohol test.
To prevent fatal road accidents under the influence of alcohol, all car and motorcycle drivers in France have been required to carry an alcohol test since 1 July 2012. Anyone travelling to France must have this single-use test with them. The tubes cost up to five euros and can be bought in France at petrol stations, in supermarkets and in pharmacies, and from autumn in Germany as well. However, only models marked “NF”, for the French standard, are accepted. Anyone who has forgotten the test will have to pay a fine of eleven euros from November if caught.
Source: http://www.tagesschau.de/ausland/alkoholtest104.html