This is, of course, merely a proposal from an advisory body about amendments to/replacement of the Official Secrets Act.
My observations suggest that political parties - particularly when in power - pay an extraordinary amount of attention to the gutter press (because this appears to be "read" by the people who make the appropriate determination in a first-past-the-post voting system). The inclusion of such a proposal in a Parliamentary bill would lead to the whole of Fleet Street campaigning for the overthrow of the government which attempted to enact it and possibly to immense condemnatory coverage of the personal ... err ... shortcomings of prominent supporters of the intended legislation.
Such legislation, of course, would only prevent publication in the United Kingdom whose government would have neither power nor influence in a post-Brexit Europe.
