My darling (teenage) dog Stella,
As you know, we don't have a fenced in yard. You are welcome to blame me for this but it should be noted that I lived here long before you did without need of one. I am however willing to cheerfully - stop eating lunch again, and take you outside at your insistence, for the third time in two hours, but let me say this: If you don't pee this time, if you insist on pursuing your hobbies i.e. eyeballing the cat, snorking up ants, or staring at airplanes - I am going to beat your six-thousand-dollar ass right out there in front of the neighbors, the trash man, and several of your dog friends. ¿Entendido?
There are some good suggestions here about how to keep cats from digging in your garden, Stella has a different suggestion but we needn't go into it.