The regularisation of irregular migrants is a human right. Having a stable immigration status is a prerequisite for leading a normal life. Article 8 ECHR protects the right to private and family life and can oblige a state to regularise an irregular migrant.
Immigrants are protected from expulsion by the right to respect for private and family life. But in certain circumstances after a criminal conviction, expulsion may be justified. The ECtHR seems to lower the level of protection in its recent case law.