For the artichokes: In an 8-quart saucepan, bring 8 cups water to a boil over medium-high heat. Juice the lemons into the water and add the squeezed lemon shells. Using kitchen scissors, remove the thorns from the tips of the artichoke leaves. Cut the artichoke stems to 1/2-inch long. Cut each artichoke into 8 wedges and, using a paring knife, remove the fuzzy choke. Place the artichokes in the pan and bring to a boil. Cover the pan and steam until the artichoke hearts are tender, about 20 minutes. Using tongs, remove the artichokes and arrange in a single layer on a baking sheet.
Place a grill pan over medium-high heat or preheat a gas or charcoal grill. Drizzle both sides of the artichokes with olive oil and season with 1 teaspoon salt and 1/2 teaspoon pepper. Sprinkle with the chopped garlic and rosemary. Grill, cut-side-down, until lightly charred, 5 to 6 minutes on each side. Set aside to cool slightly.
For the vinaigrette: In a medium bowl, whisk together the creme fraiche, olive oil, vinegar, honey, salt, and pepper until smooth.
Arrange the artichokes on a platter and serve the vinaigrette alongside as a dipping sauce.