First let me start off by saying I'm against loaning money from first world countries to third world countries. IMF/World Bank loans have been disastrous and drove billions of people around the world into poverty. Grants rather than loans should be the way to go. It is difficult for recipient countries to say they will not repay their debt because it will cause their stock markets to crash, cause people to withdraw money from banks in droves and cause hyperinflation. Iraq is starting over economically. If Iraq decided it will not repay its debt to Russia, France and Germany the impact will be minimal. Granted those countries may refuse to trade with Iraq. However, there are plenty of other countries that will trade with Iraq or buy their oil.
Legally, Iraq is responsible for the debt. However, if France, Germany, and Russia refuse to cancel at least a part of the debt, they will look really stupid in the face of the international community. Granted, I know that comes as second nature to the French, but...
If they do cancel the debt, they will look very stupid in the face of their own citizens. Europe has, for a long time, been operating under the assumption that Iraqi oil was theirs and Saudi oil was the US's. Now that the US owns both, don't expect Europe to act in "the best interest of the Iraqi people".