Washington (CNN) A day after CNN reported that the Justice Department is investigating whether Interior Secretary Ryan Zinke has broken the law by using his office to personally enrich himself, national security adviser John Bolton told the Alexander Hamilton Society in Washington that ethics rules make it hard for people outside of the government to serve.

Bolton said "things have gotten more bureaucratic, harder to get things done" since he served under President George H.W. Bush in the 1990s and blamed the difficulty, in part, on the "excessive nature of the so-called ethics checks."

"If you were designing a system to discourage people from coming into government, you would do it this way," Bolton said.

"That risks building up a priestly class" of government employees, he added.

"It's really depressing to see," Bolton said of the bureaucratic red tape.

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