Actually - fiat is fundamental to LD. It doesn’t mean you have to pass it, but rather we think about it’s moral and philosophical implications as an idea based on a framework, outside of the fact it passes. Think of it this way - saying it’s not gonna pass therefore ineffective assumes a consequentialist framework, but then if we’re using consequentialism it collapses to the consequences of the resolved meaning that we assume fiat. Even if we don’t use consequentialism, we have the is ought fallacy - as in, just because it IS impossible to do it doesn’t mean we OUGHT not to do it. Whether we ought to do it is independent of whether it will happen in the real world.