When Ryan tells Sam in "Pilot" that they can't do a dynamic entry for fears of ambushes conducted by military-trained Long Beach Lords gangsters. How does he know this? He did serve with the 75th Ranger Regiment on orders from his adopted father, so he's very familiar (or at least, knows) that there are gangs that send their men to be trained in military tactics, which is Truth in Television in recent years.
The very premise that an officer of the law is a Double Agent/The Mole for a criminal gang, not to mention that he's working behind the scenes against his colleagues to put the interest of the "family" covertly instead of the law. Though if you have watched The Departed or the The Infernal Affairs Trilogy, the idea of using a Double Agent/The Mole to infiltrate a LEO would be very familiar to you.
