The central bank's actions toward Greece occur less than two months after secret letters revealed that the ECB threatened to pull emergency funding from Irish banks if the state did not apply for a bailout, in what many saw as an overreach into the sovereign affairs of the country. The ECB later pretended that Ireland had applied for its bailout voluntarily. The letters revealed that in fact the ECB had required the Irish government to apply.

It is one thing for the ECB to require individual banks to follow certain technical rules to maintain their liquidity. It is quite another for the ECB to pressure a government by threatening an entire nation's banks with a sudden default by yanking their liquidity en masse.

That's what is going on now with Greece.

The new Greek government, led by the left-wing Syriza party, is attempting to renegotiate the terms of its bailout deal with the so-called Troika. The Troika consists of the ECB, the European Commission, and the International Monetary Fund (IMF).

Syriza wants a shift in the focus of "structural reforms" toward increasing tax collection and government efficiency and away from crude budget cuts; a "European debt conference" to renegotiate the repayment terms on the country's debt (including linking interest payments to growth and writing down some of the debt); and a reduction in the government budget surplus the country is required to run.

The Troika wants to keep the current deal, which requires the Greek to run a budget surplus (with a target of a 4.5% surplus in 2016) and implement a programme of reforms to bring government debt down from its current 175% of GDP to 124% by 2020.