The indictment of an Indian national for the attempted assassination of a Sikh separatist and dual U.S.-Canadian national 鈥渧alidates鈥 Prime Minister Justin Trudeau鈥檚 allegations that the Indian government may have been involved in the killing of a Canadian citizen as having 鈥渞eal substance,鈥 according to two of Canada鈥檚 former national security advisers.

On Wednesday, the U.S. Department of Justice announced it charged Indian national Nikhil Gupta in June in connection with a failed attempt to assassinate a Sikh separatist leader on U.S. soil.

Gupta was also allegedly connected to and working under the direction of an Indian government employee in said 鈥渕urder-for-hire,鈥 according to the U.S. Department of Justice.

The newly unsealed indictment reveals further significant details about the case, including its connection to the killing of another Sikh separatist leader and Canadian citizen, Hardeep Singh Nijjar, in B.C. in June.

In September, Trudeau addressed the House of Commons to say there were 鈥渃redible allegations鈥 the Indian government may have been involved in Nijjar鈥檚 murder.

India has denied the accusations, which spurred more than two months of tense relations between the two countries.

In a joint interview on CTV鈥檚 Question Period airing Sunday, Richard Fadden and Vincent Rigby told host Vassy Kapelos that the new information about the American charges give a certain level of credence to Trudeau鈥檚 accusations.

Meanwhile, India鈥檚 High Commissioner to Canada Sanjay Kumar Verma, also told Kapelos on CTV鈥檚 Question Period that aired Nov. 26, that India is cooperating with the Americans, but not the Canadians, because of a disparity between the information both countries have shared over the course of their respective investigations.

But when pressed at the time on whether Canada鈥檚 current national security adviser Jody Thomas shared any information with India during the nine days she visited that country in August and September, Verma said 鈥渃onversations took place,鈥 but no such 鈥渟pecific and relevant鈥 鈥渋nputs鈥 were provided.

鈥淐onversations could have allegations, conversation could have some facts of the case, but allegations and facts do not make it specific and relevant,鈥 he said. 鈥淪o we need to have those facts.鈥

Rigby said the new information about the American case, specifically unsealing the indictment, 鈥渃hanges quite fundamentally鈥 the argument from the Indian government that it is not cooperating with Canada鈥檚 investigation into Nijjar鈥檚 death because Canada has not shared enough 鈥渟pecific and relevant鈥 information.

鈥淪o I think to a considerable degree, it does validate what the prime minister said, that at the very least, there are credible allegations of Indian complicity in the killing of Mr. Nijjar in Canada,鈥 Rigby said, adding he finds Verma鈥檚 response 鈥渋nteresting.鈥

鈥淎t the end of the day, I'm not so sure it鈥檚 鈥楥anada hasn't put the intelligence in front of the Indians,鈥 but I think it's more likely a case of 鈥楥anada's not the United States,鈥欌 he also said. 鈥淲e're not a great power. And so we're treated a little bit differently.鈥

Rigby also said the prime minister鈥檚 accusations were like 鈥渢he icing on the cake鈥 after several years of strained relations between Canada and India.

Fadden 鈥 who is also a former CSIS director 鈥 agreed, saying 鈥渨e鈥檝e been told all along鈥 that Canada and the United States have been sharing evidence and intelligence with each other, so he鈥檚 鈥渙perating on the assumption that much of what was in the indictment was made available to Canada.鈥

Fadden added it confirms 鈥渢here was real substance鈥 to Trudeau鈥檚 accusations in the House of Commons.

鈥淪o I think that the Indians are now going to have to recognize, particularly if they cooperate with the United States, and we continue our cooperation with the U.S., that the intelligence and the evidence is going to flow between our three countries,鈥 he said.

鈥淏ut I think we need to be realistic,鈥 he also said. 鈥淲hat we need to do now, I think, is continue to push with our allies, to get India to realize this is not the way a democratic country based on the rule of law treats its allies.鈥

Fadden also touched on the issue鈥檚 larger implications for Canada鈥檚 now year-old Indo-Pacific Strategy.

Rigby agreed, saying the issue will become a 鈥渞eal test鈥 for Foreign Affairs Minister Melanie Joly鈥檚 attempts at 鈥減ragmatic diplomacy鈥 when it comes to the Indo-Pacific Strategy, because India is 鈥渋n many respects, the linchpin鈥 in that strategy and the region overall.

You can watch Fadden and Rigby鈥檚 full discussion in the video player at the top of this article.