you can never predict how old laws would work with modern systems - for example, in Russia you also have this rule, but after the mass persecution and censorship started the judges ruled that a post on social media, even one made before the new laws were written, is still perfect ground for conviction because it is still accessible at the time of arrest. So, how many tweets do people have? Are you going to closely follow new laws and comb through all of your post history on the entire internet every time a new law is passed?