Is it permissible for the state to prevent Muslims from extracting coral from the sea, and is it forbidden for people to extract it or buy it from them?

The prohibition of extracting coral from the sea falls under the principle of the ruler's (wali al-amr) restriction of permissible acts (mubahat), and it must be adhered to if it serves a public interest or prevents harm. If the law was not enacted for a recognized benefit, then it is not obligatory to adhere to it except outwardly, to avoid discord (fitna) and harm. Cooperating with those who violate this law by purchasing what they have extracted depends on the ruling concerning their violation: if their act is forbidden and the state does not sanction it, then purchasing is not permissible; but if it is not forbidden, or the state acknowledges their ownership of it, then there is no harm in purchasing. Such matters should be presented to the scholars of the country to assess the true nature of the situation.