Slightly clarified my comment via a parenthetical. "Non-public" in this context refers to information which would only be available to those with a fiduciary responsibility and/or a confidentiality obligation to the organization.
I was trying to avoid the use of "insider," because people tend to assume that means employees or directors, but that is not the case. Outside organizations who have, as an example, signed an NDA with the organization may learn of material non-public information, and trading on that could constitute insider trading.
> "Non-public" in this context refers to information which would only be available to those with a fiduciary responsibility and/or a confidentiality obligation to the organization.
Right, but information available to those with a confidentiality obligation can still be traded on if acquired legally. That's the crucial point. It's not enough for it to be non-public and material, you must also be in breach of a fiduciary duty (or acting in concert with somebody who is). For example, if a Boeing CEO was at a coffee shop discussing an upcoming acquisition at the table next to you, you'd be able to trade on it, even though it was confidential information not available to the general public and obviously material to Boeing's stock price.
It's not required – to my knowledge – that specific person disclosing the information be in breach of a fiduciary duty, as one could easily overcome that by disclosing to someone who discloses it to someone else, who then trades on it.
The scenario you mentioned is generally understood to be permissible, but it's not exactly clear to me why. Perhaps that the information became "public" (whether intentional or not) when discussing it in a public forum such as a coffee shop?
I was trying to avoid the use of "insider," because people tend to assume that means employees or directors, but that is not the case. Outside organizations who have, as an example, signed an NDA with the organization may learn of material non-public information, and trading on that could constitute insider trading.