Why? There is no need to abrogate Geneva and the moral high ground. The rules of engagement for uniformed Iraqi regulars should be followed to the letter vis-a-vis surrender, quarter, care, not using them as propaganda, etc. Of course if they try to off you while waving white flags, mow 'em down.
However, most of our problems are with the irregulars. They are de facto terrorists. We have no obligation to them at all under international war agreements. We need to make plain a few things to the Iraqis: if you are a civilian with weapons attempting to engage U.S. troops, you will be KILLED. If you do not follow U.S. orders in territory we are controlling, you will be KILLED. Move when you're told to move, jump when you're told to jump, line up for aid when you're told to line up for aid... but give us any cause to believe you're a guerilla and you will be KILLED.
Hopefully that'll: 1) keep pain-in-the-ass nosy civilians out of the way, and 2) make plain who Saddam's bully-boys are so they can be properly dealt with (i.e. KILLED)