I wonder what you mean and where are you pointing.
If the event is governed by the rules as defined in RRS,  (which is not clear from your question and I just presume it), then reg 20 applies as a RULE per definition in RRS
According reg 20.2.1 ...   any other than specifically permitted advertisement is prohibited. 
So, without going deep into reg 20 I think, if the flag, banner and advertisement is allowed by Reg 20, and off course not prohibited by any other rules, then it is OK.  Or?

Sadly, no one has ever asked me to advertise anything. 

Dusan, I am going deep into Reg 20.

As I read Reg 20, its prohibitions are limited to “while racing”, except for all other times it describes later. Later in Reg 20, those “all other times” are items such as backstay flags, bow numbers, etc that an event might require to be displayed at all times.

Further, as I read other aspects of Reg 20, they are likewise limited to “while racing”. 

That is the context of my tested statement. Unless otherwise restricted by a rule, boats and competitors can advertise as defined in Reg 20

(I know that SI,  NOR, CR’s are already rules and thus stating them along side of rule is redundant... but it will be helpful for the target audience of the statement) 

Hi Angelo,
My only concern is restriction of advertising in an SI.  I would always want it to be in the NOR.  If a competitor decides to enter an event based, in some part, on the fact that his sponsors are happy to subsidise that event because of the exposure they will get, and arrives only to find that the SIs significantly affect that exposure, as a judge, I would be at odds with the OA.  The NOR is the contract, if the OA then changes the contract in another, later document, that's a breach in my mind.

Ant, thanks for that. The listing of SI, NOR etc was redundant ... as they are all covered by rule.  That said, that’s an insightful point and I should remove SI from the superfluous list.

What I’m really trying to focus on is the “while racing” aspect of Reg 20. That except for the items I noted that might be required “at all times”, any limits Reg 20 places on advertising (which is very broadly defined in Reg 20) is limited to “while racing”. 

Whether or not that’s a correct reading. 

Ang, I suggest:

As I understand it, the Advertising Code is designed to be able to operate without ANY mention in the Class Rules, NOR or SI unless some particular requirement is desired.

In my opinion any rules-set (that is not closed) should not assert a general freedom or liberty, unless demonstrably necessary to resolve disputation that has occurred.

Some flags, banners etc may NOT be 'advertising' and so may escape the Advertising Code altogether.

It is probably a truism that, since the removal of the US Sailing Prescription (was it 2013?) a boat may flay any flags that it likes while racing or otherwise, unless it is 'advertising' when it is subject to the Advertising Code.

Prohibitions, such as Reg 2.2.4, and limitations such as 2.2.6 probably apply at all times.

Positive Obligations, OTOH apply only at the time stipulated.

Angelo, as a non native English speaker, I would not use the word "any", as some advertising on e.g. flags may infringe RRS 69

Willi and John, both good direction, thank you. Better to word it in a more focused manner. 

How about this?, (applying John and Willi’s input).

“WS Reg 20’s Advertising Code’s restrictions on advertising generally apply to boats and competitors only while they are racing (Reg 20.2.2 & 20.2.4). Other restrictions on advertising may exist in an event’s NOR, Class Rule or other rule for an event (see RRS definition of “Rule”).“

Angelo, 
do you prepare some teaching presentation, or want to explain /analyze the rules?  
If I would prepare a document, which is going to become another rule and it should change some otherwise valid rules, then I would use the pattern, of how to change the rule in e.g.SI   That means, referring specifically to each rule and stating the change.  That makes it clear for the reader ( competitor.)

Dusan, thank you for that input. The intent and application  is to summarize and explain, not to implement a change to a rule.

If you are going to have a "redundant" list of rules, you should also include government regulations regarding signals.

Thanks Philip.  Like I mentioned to Dusan, we are not writing new rules.  This is more for explanation/instruction purposes. - Ang