On December 8 the International Monetary Fund essentially allowed Ukraine to default on Russian debt by changing the rules of a game for the first time in 25 years.

Until 2015, Washington was relentless: pay up everyone or don’t come knocking on our door. Kyiv’s negotiating position was significantly bolstered as the IMF is now willing to deal with states that have defaulted on sovereign, but not on private creditors.

Ukraine indeed defaulted on a bond issued by its former President, Vikto...