Halachic territory

You said, and you have written more than once, that “when a person acts outside his halakhic territory out of a halakhic consideration (which is legitimate within the realm), then it is possible that the prohibition is indeed rejected (by virtue of the aforementioned consideration), and therefore if he does so he may not violate the prohibition of theft, but the boundary of his halakhic territory remains in place, since it does not depend on any halakhic considerations and there will be an extra-halakhic prohibition of crossing a meta-halakhic boundary.”
Very wonderful, but I don’t understand or don’t feel or don’t see this prohibition, where is it written? Is it a prohibition of theft or not? What prohibition is it? From which verse? Do we have to be whipped for it? Or something else?