Khomeini set the argument out systematically in a series of lectures delivered in Najaf in 1970, later published as Islamic Government, while he was in exile from Iran and had no state to apply the theory to. The lectures reason from the classical jurist's recognized authority in narrow matters, judging disputes, administering religious endowments, acting as guardian for orphans and the absent, and argue that nothing in the underlying logic actually confines that authority to those categories. If the jurist's guardianship exists because the community cannot be left without someone competent to exercise the Imam's functions in his absence, Khomeini argued, then government itself is exactly the kind of function that cannot wait, and confining the jurist to lesser matters while leaving the state to whoever holds power is an inconsistency the tradition had never actually defended, only assumed.
The 1979 revolution gave the lectures a state to test the theory against, and the constitution adopted that year wrote guardianship of the jurist into Iran's structure of government directly. The Najaf seminary, where Khomeini had taught, mostly did not follow him there. The classical confinement, guidance, teaching and judgment without direct rule, has kept a strong hold among senior Najaf jurists since, and the split between Tehran's constitutional doctrine and Najaf's more cautious reading is not a settled historical dispute but two living seminary traditions answering the same absence differently today.