The accused have been identified as Ram Kishan (55), a sepoy with the Border Security Force who opted for retirement in 2011, and Yoginder Singh (50), who is in the business of oil tankers, police said.
On the basis of inputs, Delhi Police's Crime Branch took up the matter and a list was sent to the Licensing Authority Nagaland for verification and report.
It further came to light that some of them continued holding those licenses, despite the authorities cancelling them.
During investigation, it emerged that at least three persons who were arrested by Crime Branch last year were actually part of this module. Their investigation led police to Kishan and Singh and the duo was nabbed.
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Singh himself was a client of the former security personnel, who had opened a security agency of his own in southwest Delhi's Najafgarh area after retirement and his license, obtained from Nagaland, was cancelled by the authorities, a senior official said.
The police recovered 15 arms licenses and 14 guns, including a Webley and a point 22 bore Russian-make pistol, from the duo's possession.
Efforts are on to crack the entire nexus. More arrests are likely, he added.