I often wondered as a lot of the explosives used are "cooked" from Fertiliser, why, as they did in Ireland during the troubles, do they simply not make fertilisers with a high nitrate content illegal? there by reducing amount of potential explosive available.
I heard this discussion on CSPAN where they've banned one formula of fertilizer and substituted another, which I assume is harder to make IEDs with.
However it was also mentioned that they raided a huge warehouse full of the stuff and the assumption is there are still huge stockpiles.