So a meme coin is basically like an autograph that a fan might pay a ball player to sign at a sports memorabilia convention with even less authentic value to another person since it never passed through the hand of the famous person.

Or even an autograph that passed through the hand of the famous person. Whether something is a security is governed (roughly) by the Howey test, which looks at whether the instrument involves: 1) an investment of money, 2) in a common enterprise, 3) with an expectation of profits, and 4) derived solely from the efforts of others. So you can see that something like buying a share of IBM would certainly be a security (it has all four), but buying an autograph or a Beanie Baby or an ounce of gold is not (there is no common enterprise).

The SEC was out there arguing that a lot of crypto tokens met the Howey standards, especially the ones that were using the proceeds to fund some application or program or business. Bottom of the post has a link explaining their reasoning. So the SEC was going after some of these "ICO's" that were basically offering tokens that had all the attributes of common stock (right to a share of the proceeds of some business venture, voting rights, etc.) but were just called a "token" or a "coin" rather than shares.

But pure meme coins don't have any of that. There's no common enterprise, there's no business - there's nothing but a joke or a reference, usually. They're not really that much different than baseball cards or old Happy Meal toys or anything else that is just an object, rather than an investment contract.

investopedia.com - Does crypto pass the howey test