What is the ruling on a married adulterer (muhsan) who committed penetration, then regretted it and repented, in a country that does not apply Allah's law?

Zina (fornication/adultery) is the insertion of the glans into the private parts. The perpetrator must repent to Allah Almighty, whether they are married (muhsan) or unmarried (ghayr muhsan), and whether they are in a country that applies Islamic law or not. The person who commits zina must conceal their sin and not inform anyone, and they are not required to request that the prescribed punishment (حدّ) be carried out upon themselves. The implementation of these punishments is the responsibility of the Muslim ruler. For a Muslim, sincere repentance between them and their Lord is sufficient, along with avoiding anything that leads to zina.