What is a sensible precedent?

France may allow 'first strikes' on rogue states in policy shift:

"The shift may seem strange in the light of France's refusal to approve the US-led invasion of Iraq, which was justified by American and British allegations that Baghdad was developing nuclear, biological and chemical weapons. But Paris said there was no clear proof that Iraq held such weapons and that, in any case, a military invasion would not set a sensible precedent for controlling the proliferation of WMD."