Pradyumna: "There are four varṇas, namely, the brāhmaṇas, the priest and intellectuals; the kṣatriyas, warrior and statesmen; the vaiśyas, businessmen and farmers; and the śūdras, laborers and servants. There are also four standard āśramas, namely, brahmacarya, or student life; gṛhastha, householder; vānaprastha, retired; and sannyāsa, renounced. The regulative principles are not only for the brahmacārīs, or celibate students, to follow, but are applicable for all. It doesn't matter whether one is a beginner, a brahmacārī, or if one is very advanced, a sannyāsī. The principle of remembering the Supreme Personality of Godhead constantly and not forgetting Him at any moment is meant to be followed by everyone without fail. If this injunction if followed, then all other rules and regulations will automatically fall into line. All other rules and regulations should be treated as assistants or servants to this one basic principle."
Prabhupāda: This has been practically proved in the Western countries. These boys and girls, European and Americans, they were not informed about the regulative principles in the beginning. We enforce the regulative principle when a student is serious to become initiated. Otherwise, ordinarily, in all our centers, everyone is welcome and join the chanting of Hare Kṛṣṇa mantra. Gradually, by mixing with the devotees, by being purified on the transcendental vibration of Hare Kṛṣṇa mantra, they voluntarily offer to become serious student, initiated. In this way, we have expanded. Practically the basic principle is chanting of Hare Kṛṣṇa mantra and giving them some chance to hear about Kṛṣṇa from the Bhagavad-gītā as it is.