If anyone was wondering what Nasrallah was talking about when he mentioned Wilayat al-Faqih:

Iran's Wilayet al-Faqih doctrine (governance of the religious jurist, preached in the Iranian city of Qom) was devised in the mid-1970s by Ayatollah Ruhollah Khomeini and served as the ideological underpinning of the 1979 Islamic Revolution in Iran which he led. It grants absolute authority over all matters - religious, social, and political - to a marja who has earned the title of mujtahid, a blend of judge and theologian.
Although the Wilayat al-Faqih system was successfully introduced into Iran's homogeneous Shiite society, exporting the doctrine elsewhere has proved difficult.
Its most successful adaptation outside Iran is by Lebanon's Hizbullah organization which considered Khomeini and then his successor Ayatollah Ali Khameini as the group's marja. Establishing an Islamic state in Lebanon on the Iranian model remains one of Hizbullah's ideological goals, on paper at least. But Hizbullah long ago accepted that the tiny country's multiconfessional character mitigates heavily against the creation of an Islamic state.

For greater detail, read what Cambridge University professor Ahmed Vaezi has written about it.