The news that the Obama administration is altering the United States nuclear response strategy has been greeted by the media as some sort of 'radical shift' from the Bush Administration. It is in fact nothing of the sort. From the Guardian:
The US will not use nuclear weapons against non-nuclear states that comply with the nuclear non-proliferation treaty, even if it is attacked with biological or chemical weapons, Barack Obama is expected to announce today.
However, the US president is expected to stop short of declaring that the US would never be the first to launch a nuclear attack, as many arms control advocates had recommended.
Obama will describe the purpose of weapons as "primarily" or "fundamentally" to deter or respond to a nuclear attack. But even as he limits the conditions for a nuclear strike, the president will make an exception for states such as Iran and North Korea, which have violated or renounced the NPT.
This is a classic example of clever wording with little substance. The fact that the United States will still 'reserve the right' to use preemptive action against other nations, possibly using nuclear weapons is still a direct affront to international law. As defined by the UN Charter, no nation is allowed to preemptively attack another nation unless there is a direct threat of attack (and so far, neither Iran, North Korea or any other nation state has directly threatened the United States).
To use that logic in reverse, both Afghanistan and Iraq should have the right to use nuclear weapons agains the United States given they were both attacked by it. But of course, America will never be subjected to the standards it holds others to.
This isn't to say that a less militant strategy isn't a welcome one, but it should not be confused with serious change.