In a crisis situation, is seems to me forage in rural areas would be reasonable. It wouldn't be legal, and you could face some risk dealing with the landowners, but lots of folks have livestock, crops, and other supplies handy if you are willing to sneak and/or fight for them. This may not fit the premise of the OP, but when it comes to survival, I don't follow rules that artificially limit my chances of success. It is hard enough just having to deal with natural laws.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)