In addition, songs, sculptures, architectural works, video and phono-recordings, and ship hulls can be copyrighted, among other things. But with the exception of ship hulls, utilitarian articles are not subject to copyright. Useful articles are exempted from copyright. And basically, all items of clothing and accessories are considered to be useful articles.
When it comes to knitting, what this means is that patterns (ie instructions for how to make a sweater or pair of mittens) are copyrighted. Individual stitch patterns are generally agreed to be not copyrightable, in the same category as recipes, but the written instructions that tell you how to make a finished object are copyrighted, automatically. (Older patterns may have fallen out of copyright, but that's another subject.)
However, although a pattern is copyrighted, the actual item of clothing that it describes how to make is not copyrighted. No item of clothing, whether a Vera Wang wedding gown or a baby's diaper cover, is copyrighted. No one owns any look or style or combination of elements that make up clothing. Fashion designers who work for large-scale manufacturers do not own rights to their designs, and neither does a home knitter who has created a clever pair of booties.
If a fashion designer or sweater manufacturer publishes a picture of her design, or sells her item in a shop, there is nothing at all to keep you or me or another manufacturer from looking at it, figuring out how it was made, and reproducing that same look to the best of our abilities. This is often referred to as reverse-engineering, and the new article as a knock-off. Reverse-engineering and knock-offs are completely legal in the US. If you see a hat you like in a catalog, you are free to use all your skills to make one for yourself.
So far, so good.
Everyone seems to enjoy copying some high-priced hat sold at a fancy-pants store and making it out of even nicer materials for half the price.
The flip side of this coin is that theoretically at least, a high-priced store could see your cute little hat on your knitting blog or on ravelry.com and copy you! And mass-produce them! In China! And make a million bucks! And where's your cut???!!!
So let's say that you posted just a picture of your hand-knit original hat, and another designer liked your idea and copied it. And is now selling a hat just like yours, whether through Walmart or Anthropologie, or in her etsy.com shop. Do you have a complaint? Has she infringed on your rights? Are you owed a cut? The answer is no. Why? Because fashion design is not copyrighted. You can copy the big boys, and the big boys can copy you.
So right away, someone says, ok, maybe not copyright, but maybe something else applies here. Maybe I should have patented my hat. Short answer; not gonna happen. Long answer: get a lawyer and go for it. (and it's still not gonna happen. Unless your hat turns sunlight into energy or something, it's not going to be patented. Patents are for processes. Not for ordinary items of clothing, no matter how cleverly put together they are.)
Maybe something else applies? Trademark? Trade dress? Again, the short answer is no, they don't apply to fashion design, or the design of clothing. Copying someone else's trademark, such as putting the label Gucci on a bag that is not Gucci's is infringement. Making a bag that looks like Gucci's is not.
So, okay, here's what we know for sure:
- Anyone can copy anyone else's design, style, look, shape, colors, and so on, because the design of clothing is all public domain, no one owns any of it.
- Patterns (ie instructions) for how to make a knitted item are copyrighted, and the set of instructions cannot be copied.
Footnote: From the US Copyright law:
"In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work."
(Thus, for example, Einstein's theory of relativity cannot be copyrighted, though the book in which he explains it is.)