Mix the lime juice with the salt, pepper, garlic and chile ancho powder in a heavy zip-lock bag.  Add the shrimp and marinate  (with shell intact) for one hour in the refrigerator. 

Once the shrimp have been marinated, put 6 shrimp on each skewer. Grill each skewer for about 3 minutes on each side, or until the shrimp turn red. After all shrimp are cooked, proceed to peel the shrimp and prepare to cook with the saffron and saffron chipotle salsa.