How does one prevent the use of a certain language? Are there language police? Do the Ukrainians with Russian relatives have to communicate in code?
Normally yes. In fact this law is existing for a long time but mostly for business environment. If one hears a clerk in the shop speaking Russian or colleagues at work he is supposed to report to the police. Has been this way since 2014.
The Bolsheviks and later Stalin did similar under a policy of de-Ukrainiazation. I suppose it could be called childish if it hadn’t contributed to millions of deaths, and the current rivers of blood being shed in lands that seem to have an endless thirst for it.