I guess the word I should have used was "arbitrary". It's going to be difficult to get all of my neighbors and myself to agree on all the rules for our society, I'd imagine. I have no reason to expect that they share more than the most basic assumptions about societal rules.
In the case where we move in and open up a munitions dump, either we signed an agreement not to engage in risky behavior, or we didn't. If we did, we're liable. If we didn't, then it still may be that the folks we bought the land from had, and then they're liable, since they didn't make buying the land conditional on signing the no-risky-behavior contract. Otherwise, buying that land turns out to have been a bad call for everyone else. Of course, once the dump explodes, we're liable for the damage, but as you note, we may no longer be able to pay for it.
Even when I advocate mandatory crime/injury insurance, I don't mean mandatory in the sense that I'm willing to throw people in jail for not buying it, but mandatory in the sense that I'm not willing to interact with people who refuse to buy it, or who are such bad risks that they can't afford it.
In the case where we move in and open up a munitions dump, either we signed an agreement not to engage in risky behavior, or we didn't. If we did, we're liable. If we didn't, then it still may be that the folks we bought the land from had, and then they're liable, since they didn't make buying the land conditional on signing the no-risky-behavior contract. Otherwise, buying that land turns out to have been a bad call for everyone else. Of course, once the dump explodes, we're liable for the damage, but as you note, we may no longer be able to pay for it.
Even when I advocate mandatory crime/injury insurance, I don't mean mandatory in the sense that I'm willing to throw people in jail for not buying it, but mandatory in the sense that I'm not willing to interact with people who refuse to buy it, or who are such bad risks that they can't afford it.