The Trudeau Liberals are facing criticism at home and abroad for not closing a controversial legal loophole that allows the Canadian Forces to operate alongside allies, such as the United States, that use cluster bombs.

The previous Conservative government faced widespread international condemnation because the law it used to ratify the United Nations treaty banning cluster bombs contained a controversial clause that allowed joint military operations with countries outside the treaty.

The Conservatives said Canada couldn't compromise its ability to conduct military missions with its key ally, the United States – which has not signed the Convention on Cluster Munitions (CCM) – but pledged never to use the weapons. That sparked widespread criticism that Canada was undermining the legal basis of the treaty, including complaints from the normally neutral International Committee of the Red Cross.

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In opposition, the Liberals along with the NDP pushed unsuccessfully for amendments to the bill that would categorically rule out any connection to the use of cluster bombs – tennis-ball sized submunitions that can lie dormant for decades and have maimed or killed civilians, often young children, in dozens of post-war countries.

After almost a year in power, the Liberal government has yet to change the law and faces the same criticism as the Conservatives. While the Conservatives never worried about snubbing the UN treaty system, the stance could have implications for the Liberals, who are pursuing closer ties with the world body, including a temporary seat on the Security Council.

"Canada's implementing legislation meets our obligations under the CCM and we currently have no plans to amend it," Chantal Gagnon, a spokeswoman for Foreign Affairs Minister Stéphane Dion, told The Canadian Press.

"Canada believes that our legislation, like the CCM, strikes an appropriate balance between humanitarian considerations and security interests in addressing the impact of cluster munitions."

Ms. Gagnon reiterated what the government told the annual international meeting of state parties to the treaty in Geneva last week.

Canada has a "special responsibility" to encourage countries that have not ratified the treaty to join it. "As such, we are demarching all states outside the convention with whom we operate militarily to remind them of our responsibilities as a CCM state party and to strongly call upon them to join the convention," she added.

But Canada was singled out at the Genva meeting by the international Cluster Munition Coalition for not doing enough.

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"We also call on countries to strengthen weak implementation legislation. For example, Canada's new government should amend its 2014 statute in order to prohibit assistance with the use of cluster munitions in joint military operations," said Bonnie Docherty, of the New York-based Human Rights Watch, on behalf of the coalition.

Earl Turcotte, Canada's former chief negotiator for the treaty, said he is "surprised and disappointed" by the government's inaction. Mr. Turcotte quit the federal government in protest five years ago over the then Conservative government's decision to include the controversial clause.

"I had expected far more from Mr. Trudeau's government," Mr. Turcotte said. "I will continue to advocate for amendments to avoid further loss of civilian life from these indiscriminate weapons."

The World Federalist Movement urged Mr. Dion last month to use the Geneva meeting to "initiate a process to review and repair" the cluster bomb law. The same letter reminded Dion how MP Marc Garneau – now the Liberal transport minister – argued in opposition for amendments, once proclaiming: "You're either against cluster bombs or you're not."

In August, 2015, the campaigning Liberal party told Mines Action Canada in a letter that the "ratification legislation for the treaty passed by the Conservative government did not adequately promote the stigmatization of the use of cluster bombs. Liberals believe that the legislation should have been more in line with both the spirit and the letter of the Convention on Cluster Munitions."

Paul Hannon, the executive director of Mines Action Canada, said it is "curious" the Liberals have not amended the "flawed legislation" given that Mr. Garneau and two Liberal senators "gave a very spirited, comprehensive and logical case for amending the legislation" during parliamentary hearings while in opposition.

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Mr. Hannon said he realizes the first year of a new government can be busy, so his organization is being patient.

"But the government missed a significant opportunity" at the Geneva meeting, he said, to signal "a new approach."