WITTGENSTEIN wrote:

"The forms must be obeyed", the first line of the Great Convention, is another of those famous Dune bits with meaning beyond the literal text. Simply striking a house shield with a lasgun is too blatant and simple, also background fallout radiation would be too difficult to expunge (and I think I read somewhere that house shields are too powerful and complex for a simple lasgun reaction to trigger the sub-atomic fusion). Whereas when Paul famously blew up the shield wall with nuclear weapons he was able to say that he hadn't violated the great convention, since he hadn't used atomics in a military sense, more for a demolitions purpose. Same thing when in book two they dropped a "stoneburner" on him. It technically wasn't a nuclear weapon, though it had the same force and used the same reactions.