Found some infos:

Whether or not foreigners have any criminal punishment constitute an important part for judging whether the adoption applicants have acquired the ability to raise and educate the adoptees.

In general, the CCAA shall not accept adoptive applications submitted by foreign adoption applicants who have been subjected to criminal punishment.

However, in the light of the circumstances, consideration may be given to those who have committed minor offenses and have really shown repentance and no longer committed offences ever since.