The House of Councilors approved a bill Friday detailing the domestic procedures for Japan to join an international treaty allowing the transfer of foreign inmates to serve their prison terms in their home countries.
The bill was sent to the House of Representatives and is expected to become law by the end of the current 150-day regular Diet session June 19.
The government has also asked for Diet approval for Japan's ratification of the Convention on the Transfer of Sentenced Persons, which was concluded in 1983 and took effect in 1985. Forty-nine nations have joined the pact, but none from Asia so far.
The treaty will allow Japan to transfer inmates belonging to signatory countries and to accept Japanese prisoners incarcerated in those nations.
Transfers require the consent of both countries involved as well as the inmate.
Japanese prisons held more than 2,000 foreign inmates as of the end of 2001, almost 10 times the figure a decade ago, the Justice Ministry said.
Only 130 of them belong to signatory countries and would be eligible for transfers, the ministry said.
There about 30 Japanese prisoners abroad who would be eligible for the scheme, it said.