The right to protest is governed by the Law on Right to Assembly. Concerns have been raised that the burden on protest organisers to ensure stewards are available is designed to absolve the state of its duty to properly police public gatherings. Labour unions are allowed to assemble and picket without hindrance and this year teachers held peaceful nationwide strikes. In recent times, a rising anti-immmigrant sentiment amongst some sections of society has caused tensions on the streets of Slovakia, with protestors and counter-demonstrators separated by police. In 2015, large scale anti-immigrant rallies by right-wing parties took place and police had to intervene to prevent attacks on smaller pro-migrant gatherings; some arrests were carried out. A series of large political opposition protests took place in 2016 without major incident.