At the root meaning of conservatism there are two basic defintions: One is, “tightly regulated or restricted”, and the other is, “in keeping with well-established principles”. It’s debatable which usage came first, but traditional mores tend to be more restricive of bahavior, so the connection is clear.
Now then, a conservative scoop of ice cream is one that is carefully trimmed to be exactly one scoop. The amount equal to “a scoop” has been well established, going way back to when the scoop was made. It doesn’t mean a scoop plus a little extra, because before long it’ll amount to nearly two scoops and we might run out and some kids won’t get any Ice Cream.
Now the private ownership of guns is also well established in the US. Even aside from being codified in the 2nd Amendment, it had been a prevailing social condition going back to colonial times. In this case the restraint is on well-meaning expansion of laws to supposedly protect people from guns, but which would disrupt the social order and likely lead to unintended consequences.
In this case, the emphasis on tradition goes so far as to upend the sense of being “tightly regulated”, and so gun advocates actually support a very liberal set of laws.
Similarly, economic conservatism with its oherwise “liberal” emphasis on minimal government regulation of business, is based on the historically established position here in the US. But it also contains an echo of classism, with its sense that “he who has the gold makes the rules”. There’s also the sense that the lower classes are seen as more prone to engage in corrupt bevavior and therefore more subject to restrictive social mores.
With marijuana, we have both the sense of its use being tightly restricted, as well as the sense of it being foreign and associated with minorities and the “other” and so on.
Alcohol, by contrast, is well established in Western culture. But then again, there have always been religious groups that abstain from alcohol, and so are being conservative in the more restritive sense.
