Lyman said the breach was not an isolated incident.
"It was a result of this reduced central oversight, giving contractors more responsibility for supervising themselves, and that's an invitation of corner-cutting and complacency to set in," he said.
The incident not only broke the public's trust that the government is "exercising good oversight" of its nuclear weapons facilities, according to Lyman, but he said it also has "global implications."
"If we can't even control our own nuclear weapons material, it shows what a major challenge it is around the world ... that have comparably dangerous materials but are even less protected.
And, Lyman pointed out, if the United States appears to have vulnerabilities in protecting its nuclear weapons material, "then that not only reduces our authority to criticize other countries, it raising questions about the integrity of our own security. "