In a decision of January 2015, a technical Board of Appeal of the EPO confirmed an often forgotten practical approach from the EPO to declare the citation of an ISO Standard in a claim as unclear in case there is no mentioning in the specification in regard to the chronological assignment of the cited ISO Standard (i.e. the validity date of the ISO Standard).
In particular, it has been stated that the necessary minimum information is the reference to the validity of the ISO Standard at the time of the priority date of the application. On a side note, Right to Be Heard has also been discussed, since the board of appeal included an obiter dictum as reasons for rejection (T1888/12).
Source: IP kompakt No. 3, 2015, Bundesanzeiger Publisher, Cologne