The paper which was commissioned by the Austrian Ministry of Consumer Affairs but written under the exclusive responsibility of the authors consists of three parts: The first part written jointly by the authors gives an analysis of the so-called "chapeau" of the Commission proposal on a Regulation (EU) for a "Common European Sales Law" (CESL), published as COM (2011) 635 final of 11.10.2011. The chapeau, that is the legal instrument putting into effect the eventual CESL, concerns such fundamental questions as legal basis, namely Art. 114 TFEU on the internal market, importance of the subsidiarity and proportionality principles, personal, territorial and substantive scope of the proposal, the mechanism of "opting-in" in cross-border B2C (business to consumer) transactions, its relation to the "acquis", in particular the recently adopted "Consumer Rights Directive" (CRD) 2011/83/EU of 25.10.2011, to existing Member State law under conflict-oflaw provisions of Art. 6 on consumer protection of Regulation (EU) 593/2008, and to options left to them. The second part, written by Hans Micklitz, analyses the substantive provisions of the so-called Annex I, namely the text of the CESL itself which with some modifications took over over the results of the EU expert group on a "feasibility study on an optional instrument" of 3.5.2011. It is concerned with B2C provisions on so-called "off-premises" and distance contracts with respect to information obligations of traders and withdrawal rights of consumers which are particularly relevant in ecommerce. Also the new proposals on unfair terms are discussed which go beyond the existing acquis of Dir. 93/13/EEC. The third part, written by Norbert Reich, is concerned with provisions on consumer sales and related service transactions, also based on the feasibility study with an extension to "digital content". Some of them go beyond the existing acquis of Dir. 99/44/EC, while the concept of "related service contracts" remains rather obscure and controversial. Both authors take a rather critical view towards the Commission proposal, even though they do not reject the Commission initiative ab ovo. The most important points of their detailed analysis concern the following questions: The extension of the CESL to B2B (business to business) transactions has not been explained by the Commission and does not fit well into the proportionality requirement of Art 5 TFEU. The concept of "consumer" in B2C transactions is too narrow and may create an incentive of traders to circumvent mandatory provisions in borderline cases, especially mixed purpose contracts (part B2C, part B2B) where the CESL does not contain any "safety net". The scope of precluding existing Member state law by the simple "choice" of the CESL which for the consumer is usually done on a "take-it-or-leave-it" basis should be seen as problematic; it involves a complete shift in jurisdiction on contract and consumer law matters and results in the end in a de facto "full harmonisation" which had just been rejected in the debate...