OTTAWA – Officials from Foreign Affairs and the Defence Department are defending a loophole in a much-maligned bill to ratify Canada’s participation in the international treaty to ban deadly cluster bombs.

The officials say the so-called interoperability clause is essential to allow Canada to participate in joint operations with countries that are not signatories to the Convention on Cluster Munitions — namely the United States, which has opted out of the treaty.

Brig.-Gen. Charles Lamarre, operations director for the Canadian Forces Strategic Joint Staff, says the clause protects Canadian soldiers and commanders from criminal prosecution if an ally uses cluster bombs in the heat of battle.

The clause has opened Canada to widespread criticism from across the globe, including the normally neutral International Committee of the Red Cross.

Sabine Nolke, a senior Foreign Affairs official on non-proliferation, described the issue as the most difficult aspect of the treaty negotiations.

Canada signed the convention in 2008 but has yet to ratify the treaty, a delay that has also sparked international criticism.