The Dalitz-plot of the Decay D0 \to pi+ pi- pi0 measured by the BaBar Collaboration shows the structure of a final state having quantum numbers IG JPC = 0- 0--. An isospin analysis of the Daliz-plot finds that the I = 0 contribution is about 96%. This high I = 0 contribution is unexpected because the weak interaction violates the isospin.