If it were...
If it were, why do the Sunni ulama’ condemn the oppressive rulers and caliphs, like Mu'awiya, Yazid, the wicked Ziyad Ibn Abib, Ubaidullah, Hajjaj, Abu Salma, and Muslim. If anyone claims that obedience to wicked rulers is compulsory (and some ulama’ have really said that), it would be quite contrary to the Qur'anic injunctions. Allah has frequently cursed sinners in the Holy Qur'an and has forbidden Muslims to obey them. So how is it possible that in this verse He would order us to obey sinners?
Obviously, we cannot attribute two divergent orders to Allah Almighty. Hence, Imam Fakhru'd-din Razi clearly says regarding this Holy verse that the 'uli'l-amr' must possess perfect integrity. Otherwise, Allah would not have linked our duty to obey them with our duty to obey Allah Himself and the Holy Prophet. 'Uli'l-amr' must be ordained and appointed by Allah According to the Shi’as, the 'uli'l-amr' must be free from sin and infallible.
And since no one except Allah can know the deep reality of the heart, the 'uli'l-amr' must be appointed by Allah. Thus Allah, Who ordains the prophets, also ordains the 'uli'l-amr:' An 'uli'l-amr' obviously must have the same attributes the Holy Prophet had.
In this Holy verse the word ati'u (obey) has been used twice: He says, "Obey Allah and obey the Apostle." When He speaks of 'uli'l-amr,' He does not use the word 'ati'u' again but uses the conjunction 'and' with 'uli'l-amr.' Linking the words in this way it means that 'uli'l-amr' possess the same merit as the Holy Prophet possesses, except those which are peculiar to the Prophet alone, e.g. 'Wahi' (revelation), prophethood, etc.
In short, the qualities of the Holy Prophet should be possessed by the 'uli'l-amr' except of course the rank of prophethood. Accordingly, Shi’as believe that the words 'uli'l-amr' refer to the twelve Imams, that is Amiru'l-Mu'minin and his eleven descendants, the progeny of the Holy Prophet. This verse is one of the proofs of the Imamate of the twelve Imams. Apart from this, there are many other verses supporting our point of view.
(1) For instance, the Holy Qur'an says: "He said: Surely I will make you an Imam of men." Abraham said: And of my offspring?