Which power allows Congress to impeach a president?

The ability of Congress to impeach a president stems from its non-legislative powers. Impeachment is a constitutional process by which Congress can remove a sitting president (as well as other federal officials) from office if they are found guilty of "high crimes and misdemeanors."

This process is not part of Congress's primary legislative functions but rather a specific authority granted to it as part of its broader responsibilities to oversee the executive branch and ensure accountability. Non-legislative powers include various functions such as advising and consenting to treaties and appointments, conducting investigations, and deciding issues of impeachment.

While other powers such as expressed powers (which are explicitly stated in the Constitution) and judicial powers (related to the court system) serve important roles in governance, the impeachment process is distinctly categorized under non-legislative powers due to its unique nature in terms of checks and balances within the federal government structure.