Figures in the current Syriza administration have put public and private pressure on prosecutors to investigate a list of their political enemies. When New Democracy leaders have complained to EU authorities that Syriza was politicizing judicial investigations, however, EU officials have pointed to the yearslong prosecution of Mr. Georgiou, which showed that neither of Greece’s main political parties was innocent.

Write to Nektaria Stamouli at nektaria.stamouli@wsj.com and Marcus Walker at marcus.walker@wsj.com