Can the FBI (law enforcement) easily access my messages, browsing history, etc.?

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So some backstory, my friend is acting like a dumbass, saying that NOBODY can access our iMessages and shit unless its the CIA and shit, because we were talking about carding, and I know that the FBI can easily access what we were saying if they looked for literally 10 mins, I just want to ask you guys, if a person from a law enforcement team wanted to access my iMessages and history with my friend can they easily do that?

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