U.S. Marshals have jurisdiction anywhere in the United States.

So do most all other federal agents, including the F.B.I. and C.I.A. and A.T.F. agents.

Most Federal Agents do not make arrets on the local level, unless its a felony committed in their presence or a violation of federal law.

To say that most Federal Agents are peace officers in any State is incorrect. It varies State by State and many States grant "limited" peace officer status depending upon the specific situation.

As for the CIA, they are not a law enforcement agency, with the exception of a small number of thier security folks, nor are they allowed to conduct operations domestically. They are an intelligence gathering agency.

Why do you ask?

Nebraska defines a peace officer as: "Peace officer shall include sheriffs, coroners, jailers, marshals, police officers, state highway patrol officers, members of the National Guard on active service by direction of the Governor during periods of emergency, and all other persons with similar authority to make arrests;"

Under this definition, a federal official may be a "peace officer" because they have the power to arrest. However, this is probably irrelevant because federal officials get their jurisdiction from federal law. Thus, federal agents often have similar (or more) authority than a peace officer, even if they do not have peace officer status.