The right to freedom of expression cannot be limited at the whim of a public official. They must be applying a law or regulation that is formally recognised by those entrusted with law making.
The law or regulation must meet standards of clarity and precision so that people can foresee the consequences of their actions. Vaguely worded edicts, whose scope is unclear, will not meet this standard and are therefore not legitimate. For example, vague prohibitions on ‘sowing discord in society’ or ‘painting a false image of the State’ would fail the test.
The rationale
It is only fair that people have a reasonable opportunity to know what is prohibited, so that they can act accordingly
A situation where officials can make rules on a whim is undemocratic. Decisions limiting human rights must be made by bodies representing the will of people
Vague laws will be abused. They often give officials discretionary powers that leave too much room for arbitrary decision-making
Vague laws have a ‘chilling effect’ and inhibit discussion on matters of public concern. They create a situation of uncertainty about what is permitted, resulting in people steering far clear of any controversial topic for fear that it may be illegal, even if it is not.