Validity of Commission's "soft law"

We're accustomed to block exemption regulations being accompanied by "explanatory brochures" and now "guidelines", and very helpful they are given the lack of detail in the actual regulations. They don't apply only to the motor vehicle block exemption (in which expression I now include the vertical restraints block exemption, as it's an integral part of the industry's exemption), but of course that's where we are particularly interested in Guidelines. And it's clear that Guidelines are intended to be much more legally significant than the old explanatory brochures.
Which makes this article by Wolfgang Weiß in the Journal of European Competition Law and Practice particularly interesting. As the abstract says, following the Treaty of Lisbon, is it lawful for the Commission to adopt "soft law" interpretations of primary and secondary legislation? Is it in effect amending the law, contrary to the democratic principles laid down in the Treaty? As the Abstract of teh article says,

Article 290 of the Treaty on the Functioning of the European Union (TFEU) considerably increased the legal requirements for authorizing the Commission to adopt delegated legislation. These requirements cannot be undermined by adopting administrative standards, especially if these are of considerable legal significance.

It's a piece that will certainly bear careful reading (and, if you don't already subscribe to the Journal, you can get a day's access to the article for $50), and when I have had a chance to give it proper attention I will comment some more.