Do Iran or United Kingdom have laws prohibiting their citizens to partake in diplomatic matters concerning the state?
For example. Sweden has such a law in brottsbalken 19 kap 4ยง, translated as
Swedish citizens who, without the permission of the government or the government authorized, allow themselves to be used as representatives of foreign powers in diplomatic matters concerning the state, as well as anyone who, in the alleged capacity of competent representative, engages in negotiations on such matters with someone who enters the interest of a foreign power, is sentenced for arbitrariness in negotiations with a foreign power to imprisonment for a maximum of two years or, if the kingdom was at war, a maximum of four years.
