5. The second question as to what the law must provide for, in its formulation, is a more difficult one. I would see no great difficulty in the formulation of a law which prohibits, in the very terms of article 20, paragraph 2, the particular expression that may be restricted but rather the adverse effect that the expression must necessarily have on the specified objects or interests which paragraphs (a) and (b) are designed to protect. It is the prejudice to these objects or interests which becomes the material element of the restriction or prohibition and, consequently, of the offence.