Article 1, Section 8 delegates to Congress the authority to:
“make all Laws which shall be necessary and proper for carrying into Execution the foregoing Powers . . .”
Congress has the explicit authority to pass laws that regulate Commerce, establish post roads, define and punish felonies committed on the high seas and offenses against the law of nations, and provide for the punishment of counterfeiting. Is it not “necessary and proper” for Congress to establish a means by which these laws can be enforced?
That’s a different argument than the other poster. It’s possible. Question: does the FBI ONLY have authority to do those few things?