28. (1) Whoever in respect of any drug sold by him whether as principal or agent, gives to the purchaser a false warranty that the drug does not in any way contravene the provisions of section 18 shall, unless he proves that when he gave the warranty he had good reason to believe the same to be true, be punishable with imprisonment which may extend to one year, or with fine which may extend to five hundred Taka, or with both.