OTTAWA -- One month after the terrorist attacks of Sept. 11, 2001, as Canada's ruling Liberal party introduced the country's first anti-terror bill, a government backbencher rose to speak out against it.

Liberal MP Irwin Cotler -- already a lawyer, law professor, and an esteemed international human rights advocate before entering politics -- proposed 10 changes to make the bill stronger and more democratic.

"Irwin, whose side are you on?" Cotler recalled an exasperated foreign minister John Manley asking him.

In the end, the Liberals incorporated seven of Cotler's suggestions, and two years later, the Montreal MP would be promoted to cabinet, becoming minister of justice.

Cotler's 16-year parliamentary career will formally end later this year when the current House of Commons, a bitterly divided and partisan entity, is formally dissolved and the federal election campaign officially begins.

Cotler leaves still devoted to the political party he served and believing only they can return a level of civility to Canada's shrill, bitter politics. But like many, he bemoans the inability of federal politicians to set aside their partisan imperatives and try to serve a public good.

His complaints against the Conservatives include its measures to limit debate in Parliament, showing contempt for the courts and the Charter of Rights and Freedoms, and politicizing the fight against terrorism.

Cotler, 75, is one of about 60 MPs who are quitting politics, but his departure will leave a particular void -- he's been one of the leading voices on behalf of political prisoners jailed abroad.

It was a passion that preceded his arrival on Parliament Hill, with his advocacy on behalf of Nelson Mandela, who spent 27 years in a South African prison, and Ukraine-born Natan Sharansky, who spent nine years behind bars in the Soviet Union.

Had Manley been in the Commons on June 17, two days before it adjourned for the summer, he would have had no doubt whose side Cotler was on.

"I am pleased to rise on behalf of four heroic political prisoners and their respective cases and causes," Cotler said.

He rattled off their names: Saudi Arabian blogger Raif Badawi, Venezuelan democratic leader Leopoldo Lopez, Iranian freedom of religion advocate Ayatollah Boroujerdi and Mauritanian anti-slavery advocate Biram Dah Abeid.

Each prisoner, he said, was a case study in the deprivation of liberty, of torture and the criminalization of fundamental rights, and each "oppressive regime" he named was violating its international obligations to all countries, including Canada.

"Their cause is our cause, and we will not relent until their liberty is secured."

Cotler said he will continue to advocate on behalf of political prisoners moving forward.

He wants to establish a Raoul Wallenberg centre of international justice in Canada, a consortium of parliamentarians, scholars and human rights defenders. The Swedish diplomat became the first of Canada's six honorary citizens for his role in helping saving tens of thousands of Jews in Nazi-occupied Hungary during the Second World War.

Wallenberg disappeared when the Soviet Union stormed Hungary in 1945, and was reported to have died two years later in the custody of communist jailers.

"The work with political prisoners has been one of the most inspiring things I've done even before I came to Parliament and since I've been here," Cotler said.

"Working with them and their families has been not only inspiring, but energizing."

The cases of Badawi and Boroujerdi, he said, are particularly illustrative of how dissent is being criminalized in the world, particularly in Saudi Arabia and Iran.

"They are also a looking glass into the repressive nature of the regimes that have imprisoned them."

New Democrat MP Wayne Marston, who worked with Cotler on human rights cases, including Badawi's, said his Liberal colleague will be missed because he always approached those issues in a non-partisan manner.

"He certainly brought his own slant to many files, particularly in the case of Iran accountability," said Marston. "His background, as strong supporter of Israel, gave him -- in his view -- a kind of responsibility to raise these things."

One of Cotler's last acts as a parliamentarian was to propose a 15-point plan for how lawmakers and others should deal with Iran for its human rights violations, including its recent "binge" of executions in the month the May.

Cotler, who is Jewish, said it was his parents who planted the seed for his human rights advocacy. His father, Nathan, first taught him about the Holocaust and brought him to Parliament Hill when he was 11. His mother, Fay Dubrovsky, told him that if he wanted to fight injustice, he needed to go into his community and "feel the injustice about you."

That's why Cotler's human rights advocacy will outlive his political career.

"The cases and causes with which I've been associated are not going to go away," he said.

"I'll be hitting the ground running."