Boil the fresh crab legs in a large pot of boiling salter water for 6 to 7 minutes or until cooked through. Remove all of the meat and chill.
In a large bowl thoroughly mix together crab meat, garlic powder, dry mustard, mayonnaise, egg, Ritz crackers, Worcestershire sauce, salt and pepper. Once mixed form individual patties, about 3 inches in diameter.
Once formed, coat them in the Panko bread crumbs. In a non-stick pan with a ½ cup of canola oil on medium-high heat, cook the crab cakes on each side for 3 minutes and then place the pan and finish in the oven on 350° for 6 to 8 minutes. Once cooked removed them from the oil and set aside.
For the Aioli: Place all ingredients in a bowl and whisk together until combined.
Set the crab cakes overtop of the arugula leaves and drizzle on the aioli.