I do not suspect he will do that. What he WILL do, more likely, is to use the UN treaty (which will be miraculously passed by the Senate, in the Obamacare model) to make manufacture of new weapons and -- more importantly -- ammunition, prohibitively expensive and incredibly burdensome to obtain.
He will use red-tape to starve the industry, in the same manner other dictators have used food to starve a segment of their people that they do not want.