The use of a sign on the Internet has caused infringement of trademark rights in the territory of a particular state, ifits use has a commercial effect in that state. States may adopt different standards for consideration factors forestablishing such a connection with a particular state. The first step in harmonization of applicable law at theinternational level represents the WIPO Joint Recommendation which contains provisions on relevant factorsdetermining the commercial effect, infringement and liability, remedies, etc. The Czech law does not determinefactors whether the use of the sign on the Internet is in the course of trade in the Czech Republic. Due to the strictprocedural rules, Czech courts may not proceed flexibly at imposing measures. Criteria concerning jurisdiction andapplicable law should be set at the international level in order to foresee in which state the use of signs on theInternet might become legally relevant.