The previous standardisation was based on an agreement, not a law [1]
As for why a law now when it worked without it until now
"The Common EPS Memorandum of Understanding expired at the end of 2012. The European Commission reported that all of the MoU signatories, "have met their obligations under the MoU," but that most of the signatories declined an EC request to extend the MoU beyond 2012"
Comments
The previous standardisation was based on an agreement, not a law [1]
As for why a law now when it worked without it until now
[1] http://en.wikipedia.org/wiki/Common_External_Power_Supply