When one becomes a devotee, he no longer has any duty to the Vedic regulative principles. One has many duties to perform, but if one becomes fully devoted to the Lord, he no longer has any such obligations. As stated in Śrīmad-Bhāgavatam (11.5.41) :

devarṣi-bhūtāpta-nṛṇāṁ pitṝṇāṁ na kiṅkaro nāyam ṛṇī ca rājan sarvātmanā yaḥ śaraṇaṁ śaraṇyaṁ gato mukundaṁ parihṛtya kartam

One who has fully surrendered to the lotus feet of the Lord is no longer a debtor to his forefathers, the great sages, human society, the common man or any living entity.

The Supreme Personality of Godhead nonetheless advised Prahlāda Mahārāja to follow the regulative principles, for since he was going to be the king, others would follow his example. Thus Lord Nṛsiṁhadeva advised Prahlāda Mahārāja to engage in his political duties so that people would become the Lord’s devotees.

yad yad ācarati śreṣṭhas tat tad evetaro janaḥ sa yat pramāṇaṁ kurute lokas tad anuvartate

“Whatever action a great man performs, common men follow. And whatever standards he sets by exemplary acts, all the world pursues.” ( Bg. 3.21 ) One should not be attached to any materialistic activities, but a devotee may perform such activities as an example to show the common man that one should not deviate from the Vedic injunctions.