Article 1 of European Convention on Human Rights stipulates that the States must “secure the fundamental rights and freedoms contained in the Convention to everyone within their jurisdiction”. This means that States have two kind of obligation to secure the fundamental rights and freedom.
Firstly, States must refrain from taking action that would harm your rights – the so-called “negative obligations”. For example, States may not (without good reason) prohibit a demonstration.
Secondly, States must take action to secure that you can exercise your rights effectively – the so-called “positive obligations”. For example, if it appears that counter-demonstrators plan to disrupt your demonstration, the State needs to take action to ensure that your demonstration can safely take place. It may do so by dispatching extra police officers or by guiding away the counter-demonstration via a different route.