[relknes]

The GCC talks about a natural bid being "in a minor showing 3+ in that suit and in a major showing 4+ in that suit."
Is a bid which satisfies that requirement, but says other things as well, required to be specifically mentioned on the card in order to be legal?
For example, would a bid of 2♦ promising 3+ diamonds, 3+ hearts, and 3+ spades be legal?

[barmar]

I think that falls under 6: "A convention is a bid or call that, by agreement, conveys a meaning not necessarily related to the denomination named". Promising length in other suits is a meaning not related to the denomination named. And since conventions are disallowed unless specifically allowed, and this convention isn't specifically allowed, I think it would be illegal.

[barmar]

This is analogous to 2Major bids that show that major and a minor. They were illegal on the GCC until the most recent change that added them.

[relknes]

Would it change the legality if the bid didn't necessarily show any other suits? For instance, the bid showed either 3+ diamonds, 3+ hearts, and 3+ spades with 9-11 points, or a single suited hand in diamonds with game forcing values?
This would be somewhat analogous to a 1♦ bid that shows 3+, but only has 3 with 3+ in both majors and 12-14 or 18-19 points (a feature of Standard American).

[steve2005]

relknes, on 2016-February-05, 10:48, said:

The GCC talks about a natural bid being "in a minor showing 3+ in that suit and in a major showing 4+ in that suit."
Is a bid which satisfies that requirement, but says other things as well, required to be specifically mentioned on the card in order to be legal?
For example, would a bid of 2♦ promising 3+ diamonds, 3+ hearts, and 3+ spades be legal?

I disagree with other posters.
This agreement is specifically allowed with 2♦ as a 3-suiter. It would have to promise 10+ pts. Now you would have to put some more restrictions, I doubt 7♠3♥3♦0♣ would be considered a 3-suiter but being the GCC doesn't define a 3-suiter who knows. Also 3334 would not be a 3-suiter, so you would have to put a max on number of clubs.

[kenrexford]

relknes, on 2016-February-05, 11:48, said:

Would it change the legality if the bid didn't necessarily show any other suits? For instance, the bid showed either 3+ diamonds, 3+ hearts, and 3+ spades with 9-11 points, or a single suited hand in diamonds with game forcing values?
This would be somewhat analogous to a 1♦ bid that shows 3+, but only has 3 with 3+ in both majors and 12-14 or 18-19 points (a feature of Standard American).

Fine line here. I used to want to plat 2M as 5+ in the major and either 4-card minor. That was deemed illegal. Stupid, because 5+ in the major was ok.

So, I asked if it would be OK to promise 5+ in the major and unbalamced. That was OK. This meant almost always also a minor because 2D in that approach showed both majors, which was OK. The problem hand was 6331 and 7+.

This, of course, is stupid. We were also allowed to open those 6331 and 7+ hands 1M and to use judgment. So, we got to the exact same spot, so long as we defined,a rebid as showing 6331/7+. Hence, after a 2NT minor ask, which we played, we instead called 2NT a "pattern ask" and made a 3NT rebid show the 6331/7+ hand, which amazingly never seemed right to us.

In other words, we could effectively play it, as long as we added on a hand type redundant to another opening, even if we never opted 2M with that hand, and wasted one rebid option to show that which we would never have, all to enable a treatment of a clearly natural call frequently actuallt bid by many people without the treatment because the GCC is idiotic and directors applying the GCC equally dubious.

[barmar]

steve2005, on 2016-February-05, 12:17, said:

I disagree with other posters.
This agreement is specifically allowed with 2♦ as a 3-suiter. It would have to promise 10+ pts. Now you would have to put some more restrictions, I doubt 7♠3♥3♦0♣ would be considered a 3-suiter but being the GCC doesn't define a 3-suiter who knows. Also 3334 would not be a 3-suiter, so you would have to put a max on number of clubs.

Well, the original question was asking whether this would be considered natural. I didn't even consider the possibility that it would fall into the 3-suiter category (plus, I also mistakenly thought he was asking about 1♦, not 2♦).

We had a thread a few weeks ago about what 3-suiter means. My opinion there was that since GCC doesn't define it, it's what the bridge community generally considers it to mean. I think most expect it to be something like 4441, 5431, 5440 -- one singleton or void, and the remaining cards roughly evenly divided amonth the 3 suits. I think most would not consider 6430, and 7330 would be right out.