The pumpers say insiders can't buy because they can't buy within 30 days of any news (which I believe to be rubbish and no one can show me the SEC ruling and if that were the case, no insider from IBM, MSFT, CSCO, etc., would ever be able to buy).
So, then, the converse is true assuming the pumpers are correct. If insiders may not make a transaction (buy or sell) within 30 days of news, then that means that insiders may not sell, either.
Article I, Section. 10. No State shall...make any Thing but gold and silver Coin a Tender in Payment of Debts;...or Law impairing the Obligation of Contracts [ask GM bondholders!].