Someone accused my sister of committing unlawful sexual intercourse with him. He even claimed that she got pregnant and had an abortion! We asked a Muslim female doctor to check her, and she told us that she is still a virgin and nothing of what this man claimed is true. Please note that we are living in a country that does not implement the Hudood (pl. of Hadd; corporal punishment prescribed for crimes by the sharia), can I implement the Hadd on that person myself? And how would the retaliation be (in such a case)?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

What this man did is a slander against your sister and an accusation of Zina (fornication), which entails the application of the Hadd that is prescribed for slander in Islam. He should be punished by getting lashed 80 times, as mentioned in the Quran. Allaah, the Exalted, says (what means): {And those who accuse chaste women and then do not produce four witnesses—lash them with eighty lashes and do not accept from them testimony ever after. And those are the defiantly disobedient.} [Quran 24:4]

Since the Hudood are not applied in your country, none has the right to implement them on his own, not you, nor anyone else. However, this does not mean that this person has escaped the punishment of his crime. If this (escaping the punishment) actually happens in the worldly life, then he will not escape it in the Hereafter. Allaah, the Exalted, says (what means): {…And the punishment of the Hereafter is more severe and more enduring.} [Quran 20:127]

However, if he regretted his sin and turned to Allaah, the Exalted, in sincere repentance, then his past sins will be forgiven. Allaah, the Exalted, says—after highlighting the Hadd for slander—(what means): {Except for those who repent thereafter and reform, for indeed, Allaah is Forgiving and Merciful.} [Quran 24:5]

We advise you, dear questioner, to entrust this person's affair to Allaah, the Exalted, the Just, to judge him as He wills. You should adhere to clemency, forbearing, and temperance. You should not be overwhelmed by your manly zeal and urge to take revenge, driving you to do what you may regret later. You should be thankful to Allaah, the Exalted that your sister's innocence and chastity has been proven. Otherwise, what would have been the case if the accusations were correct! We ask Allaah, the Exalted, to relieve your burden and distress and to dispose of your affair in the right way.

Allaah Knows best.