I suspect this ruling will work out very well for Ireland. US multinationals already see Ireland as an "Atlantic bridge" for getting a foothold in Europe often by placing their EMEA HQ in Dublin.

Ireland is playing up to this role and this ruling sort of hammers home the status quo that if international tech companies want to deal with the EU they will have to have separate facilities to house European data as they can't ship it all back to California.

Ireland will become the EUs primary data centre -- it has the right combination of climate, tax rates, tech presence, political diplomacy and data protection laws.

In many cases though the ruling will probably just result in an extra line on the EULA.