The duty of a pious king is described very nicely in this verse. His first and foremost duty is to give protection to the citizens from thieves and rogues as well as from ministers who are no better than thieves and rogues. Formerly, ministers were appointed by the king and were not elected. Consequently, if the king was not very pious or strict, the ministers would become thieves and rogues and exploit the innocent citizens. It is the king's duty to see that there is no increase of thieves and rogues either in the government secretariat or in the departments of public affairs. If a king cannot give protection to citizens from thieves and rogues both in the government service and in public affairs, he has no right to exact taxes from them. In other words, the king or the government that taxes can levy taxes from the citizens only if the king or government is able to give protection to the citizens from thieves and rogues.
In the Twelfth Canto of Śrīmad-Bhāgavatam (SB 12.1.40) there is a description of these thieves and rogues in government service. As stated, prajās te bhakṣayiṣyanti mlecchā rājanya-rūpiṇaḥ: "These proud mlecchas [persons who are less than śūdras]. representing themselves as kings, will tyrannize their subjects, and their subjects, on the other hand, will cultivate the most vicious practices. Thus practicing evil habits and behaving foolishly, the subjects will be like their rulers." The idea is that in the democratic days of Kali-yuga, the general population will fall down to the standard of śūdras. As stated (kalau śūdra-sambhavaḥ), practically the whole population of the world will be śūdra. A śūdra is a fourth-class man who is only fit to work for the three higher social castes. Being fourth-class men, śūdras are not very intelligent. Since the population is fallen in these democratic days, they can only elect a person in their category, but a government cannot run very well when it is run by śūdras. The second class of men, known as kṣatriyas, are especially meant for governing a country under the direction of saintly persons (brāhmaṇas) who are supposed to be very intelligent. In other ages-in Satya-yuga, Tretā-yuga and Dvāpara-yuga-the general populace was not so degraded, and the head of government was never elected. The king was the supreme executive personality, and if he caught any ministers stealing like thieves and rogues, he would at once have them killed or dismissed from service. As it was the duty of the king to kill thieves and rogues, it was similarly his duty to immediately kill dishonest ministers in government service. By such strict vigilance, the king could run the government very well, and the citizens would be happy to have such a king. The conclusion is that unless the king is perfectly able to give protection to the citizens from rogues and thieves, he has no right to levy taxes from the citizens for his own sense gratification. However, if he gives all protection to the citizens and levies taxes on them, he can live very happily and peacefully in this life, and at the end of this life be elevated to the heavenly kingdom or even to the Vaikuṇṭhas, where he will be happy in all respects.