The question has not yet been conclusively settled in Switzerland. Therefore, you first need to assume that a “third-party link” is unlawful without the consent of the author or the owner of rights. In the EU, on the other hand, this is permitted under particular conditions (ECJ, Judgement dated 21.10.2014, C-348/13). Here it is argued that a YouTube user (holder of the copyright) usually uploads their video to YouTube with the intention of making the film freely available to the public domain. When a third party then makes this YouTube film available on another website or in a social network, it can literally be viewed by a wider public. However, if and insofar as this work is freely available on YouTube, it must be assumed that the owner of the copyright has considered the likelihood of it being replayed for all Internet users as the public.