From NBC News:

Paul Rosenzweig, who was DHS’ deputy assistant secretary for policy in the George W. Bush administration, said that in the fight against international terrorism, the intelligence community has long targeted money, travel and communications. Doing that in the domestic context poses thorny constitutional issues, he said.

He said the Trump presidency shattered his confidence that the government can be trusted with intrusive surveillance authorities.

“I used to be much more sanguine about the bona fides of the executive branch, thinking that judicial and legislative oversight would constrain bad actors,” he said. “The last four years have really eroded my confidence.”