The answer, a trifle insultingly, seems to be “when it’s not erect.”
This came to my attention by way of a friend who works at an actual sex toy store (the venerable Early to Bed of Chicago, IL), which is not-unexpectedly laden with all manner of regulations regarding what they can sell and how it can be displayed. (My heart goes out to whomever makes their window displays; having done a few of those myself for a store that sold nothing more scandalous than a few suggestively-shaped citrus juicers I know how delicate the art can be.)
In an interesting spin-off venture that attracted my blogger’s fondness for legal quirks and oddities of definition, Early to Bed has helped create an independent website called FtM Essentials that deals specifically in accessories for female-to-male transgendered: chest binders, stand-to-pee funnels, and “packers” — the various kinds of harnesses, underwears, and molds designed to provide a bit of a bulge between the legs.
Where this gets interesting, at least as far as MA101 is concerned, is that FtM Essentials is not a sex toy store. You don’t have to be 18 to use their website or order their products, filtering software is unlikely to block the site (and could probably be challenged legally if it did), and so far as I can tell the products offered don’t fall under any state laws regarding sale or shipping of sexual materials.
So for this one specific purpose you can buy a big, floppy, plastic piece of man-meat, and it’s not a dildo. Technically.
That’s good news for people who want FtM supplies and don’t have a lot of freedom to go to a bricks-and-mortar sex toy store, or who wouldn’t be let in one because of their age. I suppose we could wring our hands about whether children should be trying that kind of thing out for themselves before their majority, but frankly, we’ve made growing up as a “boy” so radically different from growing up as a “girl” that I think we owe a lot of leeway to anyone who feels like he/she got assigned the wrong one.
I do find the legal precedent that a penis is only sexual when it’s erect interesting (and a bit unflattering), but I suppose our legal system’s undeniable obsession with women’s genitals focuses on their baby-making capabilities. This is only fair.
Mostly I’m just impressed by the entrepreneurial logic of it. You have to assume that there are some transgendered people out there who, just like any number of cis-gendered folk, aren’t comfortable going to a sex toy store or a sex toy store’s website, for one reason or another. Creating a deliberately desexualized online storefront specifically for them was — and you will have to pardon the pun — a textbook case of “find a void and fill it.”