Position an oven rack about 4 inches from the broiler element and heat the broiler on high. Arrange the lamb in a single layer on a rimmed baking sheet.
Finely grate the zest from both lemons and then squeeze them to yield 1/4 cup juice. In a small bowl, combine the lemon zest, juice, olive oil, and garlic. Set aside 3 Tbs. of the mixture. Brush one side of the lamb chops with half of the remaining lemon mixture and season with 3/4 tsp. each salt and pepper. Broil for 4 minutes, then flip the lamb, brush the other side with the remaining half of the lemon mixture, and season with 3/4 tsp. each salt and pepper. Broil for 3 minutes more for medium rare or 4 minutes for medium. Let the chops rest, loosely covered with foil, for 5 minutes.
While the lamb cooks, bring 1 cup water and 3/4 tsp. salt to a boil in a 1- to 2-quart saucepan over medium-high heat. Stir in the couscous, peas, and reserved lemon juice mixture. Cover, remove from the heat, and let stand until the peas are tender and the couscous has absorbed all of the liquid, at least 10 minutes.
Fluff the couscous with a fork, stir in the mint, and serve with the lamb chops.