The revisions that took effect on Monday brought about major changes in how illegally staying foreign nationals may be detained or deported.
One key change is adding an exception to the deportation rules for foreign nationals seeking asylum status.
The law allows the state to order foreign nationals to leave Japan if they overstay their visas, work illegally or are convicted of serious crimes. But for those who have applied for asylum status, deportation procedures are suspended while their claims are being screened.
The Immigration Services Agency says some foreign nationals repeatedly file applications to avoid deportation.
It says such abuse of the system has led to prolonged screening procedures and the failure to deport those who have to leave Japan under the law.
The revised law stipulates an exception to the suspension of the deportation procedure.
Foreign nationals who have applied for asylum status three or more times would now be subject to deportation unless they can provide reasonable grounds to be recognized as refugees.
The new regulation also enables authorities to deport those who have been given a prison term of three years or longer in Japan, without suspension, as well as those who are recognized as terrorists.
Another key point is a review of the rules for detention in immigration facilities.
So far, those given a deportation notice, those under examination for deportation and those who refused to depart the country after being ordered to do so were detained in principle in immigration facilities.
It is said that this often led to long-term detentions, resulting in health problems for detainees.
The Immigration Services Agency also said the system of provisional release for health and other reasons did not have sufficient measures to prevent people from fleeing as their personal guarantors were not legally obliged to do so.
The revised law allows those facing deportation to live outside detention facilities if approved, under the oversight of authorized supervisors. The supervisors are required to assess how those under their supervision are living in Japan.
Supervisors are obliged to report to immigration authorities when they find illegal working or possibility of fleeing, or when asked by the authorities for information. They face penalties if they fail to do so.
Those foreign nationals are also obliged to make a report on their lives to immigration authorities, who will review every three months whether there is a need to detain them again.
The system of provisional release from detention facilities will now be limited to cases of health reasons.