This phrase means one must be careful when appointing a guardian, and make sure someone is watching them as well. Quem vigia os vigilantes? O que os vigilantes vigiam? Até que os vigilantes venham Vigilantes odeiam outros vigilantes Escolha a tradução mais próxima da frase latina acima.
They have their knees digging into your back, they are talking loudly and the light from their phone is distracting you. What do you do? Turn around and SHHH!