The bill was approved on January 31 despite calls by human rights groups for war crimes trials.
Adrian Edwards, the chief spokesman for the United Nations Assistance Mission in Afghanistan, told RFE/RL that the rights of victims of war crimes should be at the heart of national reconciliation and any efforts to grant impunity.
"It's crucially important that the victims [of war crimes] are not forgotten in this debate," Edwards said.
"It really is up to the individual to decide whether they can forgive or not. And in that sense, for the [Afghan] National Assembly or any other body to suggest that there should be some blanket forgiveness -- we don't think that's the right way to go. We need to hear the voices of the victims too. And if this process [of national reconciliation] is going to be successful, their voices will have to be equally heard."
Some Afghan legislators have said the bill is an attempt to bring reconciliation and peace to the country.
But human rights groups say bringing war criminals to justice -- including some members of parliament and senior government officials -- is vital for peace.
(with additional reporting by dpa)