Germany's Constitutional Court ruled Tuesday that the European Central Bank must clarify a key bond-buying scheme to support the eurozone economy is "proportionate" or else Germany's Bundesbank central bank may no longer participate. The Bundesbank will be barred from participating in the "quantitative easing" (QE) asset purchase programme in three months' time "unless the ECB Governing Council adopts a new decision that demonstrates in a comprehensible and substantiated manner that the monetary policy objectives pursued by the ECB are not disproportionate," the court said in a statement. tgb/mfp/jh