AIM 5-5-6

Pilot. Promptly complies with headings and altitudes assigned to you by the controller.

Questions any assigned heading or altitude believed to be incorrect.

If operating VFR and compliance with any radar vector or altitude would cause a violation of any CFR, advises ATC and obtains a revised clearance or instructions.

Controller. Vectors aircraft in Class A, Class B, Class C, Class D, and Class E airspace: For separation.

For noise abatement.

To obtain an operational advantage for the pilot or controller.

Vectors aircraft in Class A, Class B, Class C, Class D, Class E, and Class G airspace when requested by the pilot.

Except where authorized for radar approaches, radar departures, special VFR, or when operating in accordance with vectors below minimum altitude procedures, vector IFR aircraft at or above minimum vectoring altitudes.

May vector aircraft off assigned procedures. When published altitude or speed restrictions are included, controllers must assign an altitude, or if necessary, a speed.

May vector VFR aircraft, not at an ATC assigned altitude, at any altitude. In these cases, terrain separation is the pilot's responsibility.