"If he wishes to return knowing he would be held accountable and also able to present a defense, that is his decision to make," Clinton said.
"In any case that I'm aware of as a former lawyer, he has a right to mount a defense," she continued. "And he certainly has a right to launch both a legal defence and a public defence, which can of course affect the legal defence.
She also argued that returning to the United States would allow Snowden to continue the "debate" he wished to start by leaking the information.
"Whether he chooses to return or not is up to him. He certainly can stay in Russia, apparently under Putin's protection, for the rest of his life if that's what he chooses," she said. "But if he is serious about engaging in the debate then he could take the opportunity to come back and have that debate. But that's his decision."