All three desert tortoise species are now protected: the MOJAVE DESERT TORTOISE, the SONORAN DESERT TORTOISE and the SINALOAN DESERT TORTOISE. As of 2018, the Mojave species in particular was upgraded to "critically endangered" status by the Tortoise & Freshwater Turtle Specialist Group in their book Turtles in Trouble. But all desert tortoise species are showing alarming declines in population. As a result, it's illegal to take any desert tortoise from the wild. They are so long-lived, however, that many of the ones taken from the wild decades ago have outlived their keepers and need new homes. Additionally, those captive oldsters will often have bred in captivity such that a new generation of younger captive DTs now need homes as well. The reasons most of these captives cannot be returned to the wild are complex and numerous but David Danelski in his Press-Enterprise article does a good job of explaining this odd situation. Long story short, if you live in one of the desert tortoise's native states (Arizona, California, Nevada or Utah) and if you have a yard that you wouldn't mind converting into a desert tortoise habitat, you can adopt one. Here are the official entities that legally adopt out desert tortoises:

• Arizona Game and Fish Dept
• California Turtle & Tortoise Club
• Nevada's Tortoise Group
• Utah Division of Wildlife Resources

One of the most all-inclusive desert tortoise care pages on-line used to be the Arizona Game and Fish Department’s Desert Tortoise adoption pages. It’s still pretty decent so I’m linking to it here. Additionally, though, I’m including this link to the archived older version which includes much more but isn't configured for smaller screens. Current | Old Version

Diet
Captive DT Diet | Native DT Food Plants

Burrow Construction
Above Ground Above Ground | Underground Underground

Additional Resources
One other DT caresheet that is highly recommended is the one at the Don's Desert Tortoises website. Included is a wealth of information on every aspect of DT husbandly plus photos of proper habitat for hatchlings and grown tortoises.