'Knowing' you will put an offer to buy a company is insider information. The assumption here is he has been acting on this information recently and it was part of his plan.
Unless you think he just woke up today and said: You know what, I'm going to buy Twitter! Which, I mean.. given Elon maybe that's what happened. But if it was premeditated then he has clearly been acting on insider information.
If you have no intention to actually follow through and it's a false promise, that's a pump-and-dump. It's securities fraud, but it's not insider trading.
If you have an intention to actually buy and make a good faith effort and fail, that's just business.
Duh, but they are not acting on the insider information.
Elon is. He bought shares, then put in an offer which drives his existing shares up. Perhaps you can argue until he sells them he isn't acting.. perhaps.. but if he sells them today, are you still telling me he isn't acting on insider information?
From the SEC website: Who is an insider? An “insider” is an officer, director, 10% stockholder and anyone who possesses inside information because of his or her relationship with the Company or with an officer, director or principal stockholder of the Company.
A principal shareholder is a person that directly or indirectly owns or controls more than 10% of any class of voting shares or securities of a company. The principal shareholder has the authority to vote using those voting shares.
Elon has less than 10% share (9.2%), so he's not an insider. Probably he stayed under 10% because of this law.
