During the Brooklyn bridge station level, you'll find a gang of Rooks controlling the upper level. They're wearing blue sweaters and blue beanies. Either kill or incapacitate all of them and then make sure your inventory is full (can be any items). Then speak with the gang leader El Rey at the far end of the upper area and ask for a LAM. JC should laugh and unlock this achievement.
Tip: If you're carrying LAMS, make sure you have the maximum amount otherwise El Rey will give you the LAM and JC won't laugh. An easier alternative is to just drop your lams and fill the space with something else.