Trademarks in smells?
There was a 2003 case in Europe, Sieckmann, that may have made trademarking smells difficult.
The Sieckmann case makes reference to various European trademark registries beginning to see difficulties with registering smells. The UK Registry rejected an application to register the 'smell, aroma or essence of cinnamon' for furniture products. And in the Sieckmann case itself, the European Court of Justice gave a ruling on the registration of smell marks. The court confirmed the principle that non-visual signs could be 'trademarks' and thus registered, providing the sign was distinctive. However, the case turned upon how smells might be represented graphically. By rejecting all of the main possible modes of representation - by a chemical formula, by a description in written words, by the deposit of an odour sample or by a combination of those elements - the ECJ has made it well-nigh impossible to register smell marks for Europe in the future.
Citing Theofrastus on the intoxicating and all-powerful scent of the rose, Maniatis observed
'perhaps it is better for people to avoid trademarking scents, and, instead, let the scent of the rose fulfil its superb function, irrespective of its name, even when it can indicate origin.'
By Sieckmann, the European Court has effectively removed scents from the trademark system.
[Ralf Sieckmann v. Deutsches Patent- und Markenamt (C273/00)  E.C.R. I-11737 (ECJ);  Ch. 487;  R.P.C. 38 ECJ;  E.T.M.R. 37 ECJ]