The Dutch provision implementing the definition of the professional diligence requirement - article 193a(1)(f) of Book 6 of the Civil Code - initially lacked the normative criteria and it still does not comprise the explicit reference to the good faith principle. Besides, the legislator has, in his explanatory documents, underlined the relevance of codes of conduct to this requirement, especially when consumer associations have been involved into their drafting. In the absence of alternative benchmarks, courts and supervisory bodies will assumingly often conclude that a code matches the level of protection aimed at by the UCPD. As it is, in the domain of public enforcement of the UCPD, codes of conduct largely set the professional diligence standard. One of the two Dutch public authorities in charge of the enforcement of the UCPD - the Consumer Authority (CA), which has merged into the Authority Consumer and Market (ACM) on 1 April 2013 -fills in the professional diligence requirement by referring to codes of conduct. In two separate cases, it considered the requirement was breached because the trader had failed to abide by the standard of conduct laid down in a code.
In its decision concerning the Nederlandse Energie Maatschappij (NLE), the breach of the requirement of professional diligence was not only assessed in reference to the Consumer and Energy Supplier Code the trader had signed up to, but also to the Currence Rules & Regulations. According to the CA, the NLE had violated a ban on cold callers asking new customers to set up a direct debit, which was contained in both sets of rules. The NLE defended itself by contradicting that the Consumer and Energy Supplier Code encompassed such a ban and by arguing that the Currence Rules & Regulations should not define the level of professional diligence it ought to attain. In the appeal procedure, the court agreed that the CA's (extensive) interpretation of the Consumer and Energy Supplier Code was wrong. The Administrative Court declared, however, that the public body was right to found its decision on the Currence rules since the Telemarketing Code, which is part of the Consumer and Energy Supplier Code, states that telemarketers will abide by the self-regulatory rules in place. The Currence rules qualify as such rules. What is more, by making use of a service owned by Currence (direct debit), the NLE is contractually bound by the Currence rules (through its contract with the bank). Having regard to the concreteness of the rule, the question then arises why the CA did not base its decision to fine the NLE on article 6(2)(b). The most plausible explanation would be that the CA did not consider the NLE to have indicated in a commercial practice to have undertaken to operate in accordance with the Currence rules (as is required by this article). In this case, the Currence rules helped the CA kill two birds (an unfair practice and a violation of 'confidence inspiring' self-regulatory rules that is not being caught by article 6[b]) with one stone (the professional diligence requirement).
The same goes for the Celldorado case concerning unfair SMS practices, where the general clause was used to tackle the infringement on an open-ended provision of the SMS Code of Conduct by a code signatory having publicly undertaken to be bound by this code (article 6[b] only deals with the breach of firm and verifiable commitments). The CA found that Celldorado, a SMS services provider, had acted in breach of an information duty that was deemed to equate to the expected level of professional diligence. Celldorado denied the breach of the code and appealed the decision. In its decision on appeal, the Administrative Court emphasized the factual and normative dimension of the professional diligence test and the necessity to test the trader's behaviour against the legal standard. It stated that acting in compliance with a code did not automatically amount to fair conduct in the sense of the UCPD. However, from the CA's point of view, there was no compliance with the code. Hence Celldorado's and, allegedly, the code owner's interpretation of the code diverged considerably from the interpretation conferred by the administrative authority on the open-textured commitments laid down in the SMS Code.
-  Dutch Parliamentary Papers 2006-07, 30928, No 3, 16-17.
-  The other supervisory authority being the AFM (cf. n 19).
-  Celldorado (case 510, 17 June 2010) s. 333ff followed by CFI Rotterdam 19 April 2012, ECLI:NL:RBROT:2012:BW3358 and Nederlandse Energie Maatschappij (case 527, 6 September 2010) s. 308ff followed by CFI Rotterdam 12 November 2010, ECLI:NL:RBROT:2010:BO3707, s. 2.3.2.
-  CFI Rotterdam 13 December 2012, ECLI:NL:RBROT:2012:BY6184, s. 15.3. See also CFI Rotterdam 12 November 2010, ECLI:NL:RBROT:2010:BO3707, s. 2.2.3.
-  CFI Rotterdam 13 December 2012, ECLI:NL:RBROT:2012:BY6184, s. 15.4.5.
-  CFI Rotterdam 19 April 2012, ECLI:NL:RBROT:2012:BW3358, s. 21.5 and s. 23.2-3.
-  Opinion of the Adviescommissie bezwaarschriften (BAC) of the Dutch authority in the Celldorado case (case 510, 7 December 2010), s. 5.20: acm.nl/nl/publicaties/publicatie/7436/Besluit-op-bezwaar-met-BAC-in-de-zaak-Celldorado/. The trader failed to substantiate this argument: CFI Rotterdam 19 April 2012, ECLI:NL:RBROT:2012:BW3358, s. 23.3.