Comment by anonymousDan

For non-EU readers, note that taxation is explicitly not a competency of the EU (i.e. Ireland can set its tax levels to whatever it wants). The only thing in question here is whether it was applying the same taxation rules to all companies, as granting special exceptions to certain companies could be viewed as state aid (which is not allowed). Ireland claimed it wasn't, the current (over-)ruling says otherwise. This case is also specific to tax rules from many years back. AFAIK the rules have subsequently been tightened and the exemption no longer exists.