1. All guns are always loaded...
Such a statement is not a rule, but, more properly a 'maxim', that is,a handy phrase that stimulates the memory and thereby increases safety.
A rule is a means of controlling behavior, a prescribed action, not an absolute statement of a condition or situation. In order to be a rule, the statement would have to be of the form, "Treat all guns as if they are loaded until proven otherwise." That would then satisfy the criteria for rules, as opposed to maxims.
Of the thousands of students and instructors I've trained over the years, I get one every once in a while that insists he's correct in stating, "all guns are always loaded," until I ask him (almost always male) how he cleans his gun. He invariably replies that he unloads his gun before proceeding. I then remind him his gun is still loaded, as, he said, all guns are always loaded. If a 'rule' is to be considered as true, it must not arrive at a logical contradiction and, if all guns were always loaded, it would be impossible to clean an unloaded gun, as all guns are always loaded. As we know guns can be unloaded, the rule that 'all guns are always loaded' fails the test of non-contradiction and is a logical fallacy.
The student invariably winces, and in the face of logic, admits the truth, that no, all guns are not always loaded.
We all have a lot of respect for Jeff Cooper. Stephen Wenger also posts this as his 'rule' one. I always use the maxim as a memory aid for students, as it is a snppy little witticism that does stick in the mind, but in the end, it's an irrational fallacy, as all guns are not always loaded.
The NRA rules on firearms handling are a better structured set of conduct standards as they provide a logical, overlapping set of true rules, not maxims, that prevent the wrong person from getting shot. You can violate one or two rules and if you follow the rest, no one's hurt. It's when you violate the first three simultaneously that the wrong person is shot.