(CNN) – Face masks aren't mandatory everywhere, but strict rules on wearing them have been enforced in the Czech Republic -- even for nudists. "Unfortunately, many of the sunbathing citizens were gathered in large groups, and some were not wearing face masks.," a police statement said. "Upon the arrival of the police, everyone agreed to respect the government regulation [that face shields are compulsory outside the home]. The statement said a subsequent police patrol found that of 150 people encountered, only half needed reminding about masks. “That however will not happen until everyone starts to dutifully respect the rules.”