A superficial reading of the rules says no.

If you look at page D60 of the manual you find this:

Pre-alerts

At the start of a round or match, Pairs should acquaint each other with their basic system, length of their 1-level opening bids, the strength and style of their opening 1NT and any unusual self-alerting calls as defined above that may catch their opponents by surprise (e.g. doubles that are neither for penalty nor for takeout, or high-level transfer pre-empts).

I would deem that if a pair has pre-alerted that they're playing a canape system; then the opening bid shouldn't be alerted (but I would never penalise anyone for alerting one). If a pair hasn't pre-alerted their basic system then the ethical burden is on them to alert it.

A close analogy is the precision 1D opening bid, which (usually) can be as short as 0, 1, or 2; depending on the flavour of precision being played. Typically the sequence 1D 1x; 2C can have longer clubs or longer diamonds. This rebid is obviously (and commonly) alerted, but the  inference that 1D could be canape initially stems from the idea that the promised suit length was initially 1+.

But without a pre-alert, it would be a reasonable assumption that a pair who open 1S would have either 5+ spades or possibly a 4 card S suit with a strong NT style hand. it would be unfair to have people assume this and then actually just wheel out some 4xx5 or 4xx6 shape on them later in the auction. They might misjudge the distribution around the table because of this.

Coming back the the operative sentence in 30.2.2 "The bid is natural, but its meaning is affected by other agreements, which your opponents are unlikely to expect." - I think this shows a clear link between pre-alerting the canape nature of bids and not alerting them (but alerting the subsequent canape call). But it would definitely be a form of active ethics to alert a "natural" bid with an unexpected meaning, and as a player it's what I encourage all of my opposition to do.

Thanks Brad.

That makes a lot of sense.

It seems odd that if the canape style has been pre-alerted then the rebid is to be alerted. You would think that the pre-alert would cover the rebid as well as the opening bid.

Thanks Giles.

Are you assuming the canape style has been pre-alerted?

I'm imagining a bidding sequence - 1H P 3H P 4H all pass. As a defender if I don't know about canape I wouldn't pick declarer's shape to be say 1426.

Regards

Hi David

In that situation the opponents should "delayed alert" after the bidding ends and before the lead is made

Failure to do that is misinformation and warrants an adjustment if there is damage

But the tricky one is a sequence like 1H then 1S by the opponents who end up declaring without any more bidding from the opening side.

Then the defending side can't "delayed alert"

Because of that I believe the opening bid of a canape sequence  should be alerted in any situation where pre-alerting is not  practical

"Active ethics" trumps "work to rule"