After spending six years as U.N. human rights chief, Navi Pillay strongly urged Japan to investigate “every allegation of sexual slavery” and “prosecute perpetrators” through a rare statement and then again a media interview last month.

Her perspective and interest in the issue of the “comfort women” stand out because they demonstrate the international community’s human rights standards and growing demands for Tokyo’s action.

In the Aug. 6 statement, Pillay expressed “profound regret that Japan has failed to pursue a comprehensive, impartial and lasting resolution of the issue of wartime sexual slavery” and thus the human rights of the victims “continue to be violated decades after the end of the Second World War.”

During an Aug. 31 press interview, she criticized the Japanese government and ultra-conservative forces, saying she was “shocked” that some civic groups even raised questions about the genuineness of the victims while no progress was being made at all on the resolution of the sex slavery issue. Pillay also repeatedly emphasized that the U.N. has recommended Tokyo offer an apology and compensation through the Human Rights Council’s Universal Periodic Review and other various treaty organizations and human rights experts.

The international community has been rallying behind the cause. Since the U.S. House of Representative adopted a resolution calling for Japan’s acknowledgement, apology and redress for its wartime sex slavery in July 2007, similar measures have been taken in the Netherlands, Canada, the European Parliament and elsewhere. In response, the Japanese government has been insisting that the issue has been resolved. At the UPR meeting in June 2008, it made a case using logic that is most favorable to its position, such as involving the 1993 Kono Statement, the 1995 Asia Women’s Fund and previous accords.

Yet the Japanese government’s argument failed to calm the criticism. First, the Kono Statement came after the historic public testimony by victim Kim Hak-sun in 1991, the unearthing of documents by professor Yoshiaki Yoshimi in 1992, and an ensuing 20-month investigation that led Tokyo to acknowledge its military’s involvement in the forced mobilization of the women. Upon its inception in 2006, however, the Shinzo Abe administration set out to deny “the forcibleness in a narrow sense,” downplaying the landmark statement as mere political rhetoric.

Second, the Asia Women’s Fund was simply a tool for Japan to disregard the victims’ demands for a formal apology and compensation and evade its state responsibility for what constitutes war crimes against humanity. In 1998, U.N. Special Rapporteur Gay McDougall issued a watershed report calling for the establishment of a “new administrative fund with appropriate international representation” since the Asian Women’s Fund “does not in any sense provide legal compensation.”

Third, contrary to Japan’s claim, the 1951 San Francisco Peace Treaty could not clear its legal responsibility for sex slavery, because the pact was signed when Korea’s signatory status was excluded in the first place, with Japan taking the lead. The 1965 agreement that normalized bilateral relations also address neither crimes against humanity involving Japan’s state power nor any illegal acts directly linked with colonial rule. The 2010 joint statement by intellectuals in Korea and Japan, a 2011 ruling by the Korean Constitutional Court and a 2012 verdict by the Supreme Court here all reaffirmed internationally recognized historical truths.

Against this backdrop, Tokyo’s argument that its forced annexation of Korea was legal, as well as its sexual enslavement of young women who lived in regions it invaded including Indonesia during the Pacific War, violates international law as follows.

First, these actions constitute crimes against humanity, which means cases in which anti-human acts such as killings of civilians, extermination, slavery-like exploitation, rape, sexual enslavement are committed extensively or systemically regardless of the region’s domestic law, in not only wartime but also peacetime.

Second, it constitutes sexual slavery, which breaches the 1930 International Labor Organization Convention concerning forced labor, ratified by the Japanese government in 1932. In May 2014, Seoul officially demanded Japan’s resolution of the issue at an ILO panel session.

Third, it runs counter to the Article 46 of the 1907 Hague Convention Respecting the Laws and Customs of War on Land, which prohibits rape during wartime.

Fourth, it violates the 1910 Convention for the Suppression of White Slave Traffic, which Japan ratified in 1925, the 1921 International Convention for the Suppression of the Traffic in Women and Children, and the 1926 Slavery Convention, which works as customary international law.

Fifth, Japan’s war responsibilities remain unresolved since the mobilization of “comfort women” is applicable to the Convention on the Non-Applicability of Statutory Limitations to War Crimes and Crimes Against Humanity, adopted by the U.N. General Assembly in 1968.

Given that today’s international human rights law was born out of the soul-searching on the aggression and atrocities committed by Japan and Germany during World War II which marked extreme devaluing of human dignity, Pillay’s perception on the “comfort women” is in line with her statement issued while serving the International Criminal Tribunal for Rwanda that “From time immemorial, rape has been regarded as spoils of war. Now it will be considered a war crime. We want to send out a strong signal that rape is no longer a trophy of war.”

In this vein, the Japanese government must atone and compensate the victims by realizing that sex slavery constitutes crimes against humanity and a breach of human rights which are a universal value. Ultimately, perpetrators should be held accountable, and education conducted to prevent a future relapse. I urge Tokyo to give the aging survivors one last chance to bring justice. Japan must bear in mind that it will leave the biggest, irreparable stain in human society if it fails to respond to the requests of Pillay and the overall international community.

By Doh See-hwan, Research fellow, Northeast Asia History Foundation