There is a lot of confusion about the availability of Genetically Modified (GMO) seeds for use in home gardens. The source for some of that is a misunderstanding of what hybrid seeds are as compared to GMO seeds.
In hybrid seeds, the patented genetics are a result of crosses created by moving pollen from one variety of a particular species of a plant to the stigma (female part) of a different variety of the same kind of plant. For example, the pollen from a disease resistant tomato plant might be placed on the female flower parts of another kind of tomato that has better flavor, resulting in seeds that reliably become disease resistant plants that make tasty tomatoes. This is a controlled version of something that could actually happen in nature.
In genetically modified seeds, bits of DNA from one kind of organism are spliced into DNA of another completely different kind of organism. For example, a bit of bacterial DNA might be added to the DNA of corn, with the goal of managing a persistent problem with corn ear worms in a way that requires a lot less pesticide than usual.
Since the process for development and production of the GMO seeds is costly, the companies that make these seeds have placed all kinds of restrictions on how they are sold and managed. Farmers who want to grow these seeds have to sign great piles of paperwork and promise to not save seeds to grow for next year's crop. I have a hard time imagining that this level of control is going to be feasible in the market of home gardeners. We tend to be a little unruly and to not always follow instructions!
However, we could end up growing GMO crops by accident. Several seed companies that sell to the gardening public have taken a "safe seed pledge," and they are testing their seed for inclusion of GMO contamination. Baker Creek Heirloom Seeds reports (in its 2013 catalogue) that it has found GMO contamination in some batches of garden crop seed (that it then rejected).
Technically, it probably would be illegal to grow that seed, even if the genetically engineered parts were there accidentally and unknowingly, because those special genetic combinations are owned by the corporations that developed them.
Any gardener looking to avoid growing GMO crops should probably buy the most-likely-to-be-affected seeds from a company that is testing seeds specifically for that accidental contamination. I've been looking for a comprehensive list of GMO crops currently being grown and haven't found one, but I do know that the list includes corn, soybeans, beets, zucchini, potatoes, rice, wheat, eggplants, canola, cotton, alfalfa, plums and papayas (not really row-crops), and probably more.
Many of these are not being grown in people's yards, but gardeners sometimes grow some pretty odd things. I , for one, have grown both rice and wheat, just for the experience, and alfalfa is sometimes used as a long-term cover crop.