This is one of the most ridiculous concepts ever. In personal terms if a mugger uses a truncheon then all you can use is a truncheon; if you use a gun to defend yourself then that is not proportional and you are wrong. See how silly that is?
Or how about if some high muckity-muck in the DoD wants to try and contain the escalation of conflict. So he decrees that US forces can only up the ante if the enemy does it first. This nimrod, by his ludricous decree, just denied the US the advantage of initiative.
Think no one in the DoD could be that stupid? Ask Robert McNamara since that is how he ham-strung US forces in VietNam. Oh they are building an SA-2 site or two or three? Well until they fire on US warplanes nothing can be done or we might kill a Russian advisor. All McNamara did was prolong the war until America grew tired of it, aided and abetted by the media. So over 50,000 American lives were lost along with countless South VietNamese lives.
And the talking heads like Kofi Annan are suggesting this very concept in regards to Israel's attempt to stop the rocket attacks on its citizens that are being launched from south Lebanon and Israel's efforts to find their kidnapped soldiers. Needless to say, a return to a status quo that is advantageous to Hezbollah is not in Israel's interest and should be avoided at all cost.