Here is Nadler's exchange with Mueller:
Update: The statement from the office of the DNI further shooting down Nadler's original claim:
The statement that a single analyst can eavesdrop on domestic communications without proper legal authorization is incorrect and was not briefed to Congress. Members have been briefed on the implementation of Section 702, that it targets foreigners located overseas for a valid foreign intelligence purpose, and that it cannot be used to target Americans anywhere in the world.
Office of the Director of National Intelligence Public Affairs Office