Legal bounds for non-conventional trademarks

What are the limits of compulsory trademark features in selected countries following the continental and common law? In my work I examine the positive and negative trademark registration issues in Common and Continental Laws, which one is more attractive from the point of registration latitude for global businesses. I compare and explain which countries under different law systems are more favourable from the angle of trademark registration and compare four of them: Russian Federation, Czech Republic, the USA and Great Britain. The main trademark features I examine are the regulations regarding what can be registered and what cannot be registered in considered countries. While the special accent is made on how these requirements are applied to registration of non-traditional signs, specifically color, sound and smell.