Well-known mark is a brand that is well known by the public because of its reputation by their owners by way of investment and promotion in different countries, with evidence of its trademark registration. In this thesis we will consider two formulation of the problem thait is, how the legal protection of wellknown mark by legislation Indonesia and how violations in bad faith in the Supreme Court decision No.557K/Pdt.Sus-HKI/2016. The protection of a brand not absolute. If there are those who feel these brands have a similarity in principle with his own brand, then the owner of brand can submit a action brands to the commercial court by reason of the bad faith of the brand owner to register his trademark. In order to provide certainty and legal protection, then Indonesia as WTO members have ratified TRIP's and the Paris Convention which specifically regulate matters relating to IPR. The research method used in this thesis is a normative legal research methods where primary legal materials used include Supreme Court Decision Number 557K/Pdt.Sus-HKI/ 2016 and Law No. 15 of 2001 on Marks. Based on the results of the Supreme Court of Cassation Decision No. 557K / Pdt.Sus-HKI / 2016, the judge stated in this case the defendant registered the brand Lavera are registered in bad faith by piggybacking fame Lavera brand owned by the Plaintiff. In bad faith by registering the Defendant can dibuktinya Lavera brand, as previously Defendants have the brand GINVERA already registered and successively extended.