The fate of the Eurozone, it appears, could hinge on tiny Cyprus. And at least one Am Law 100 firm is in the thick of it as the drama plays out.

Lawmakers in the divided island nation vetoed a European Union–backed "bail-in" agreement earlier this week that would have pumped $13 billion into Cyprus while levying a tax of between 6 and 10 percent on accounts held in the Mediterranean island country. The controversial tax would have raised $7.5 billion, with the remaining $5.5 billion of the total to be supplied by the European Union and International Monetary Fund.