Once you begin your education in the College of Engineering, attendance at any institution other than UC Berkeley requires permission. If you wish to take courses at another school during the summer (or in a semester that you are not enrolled at UC Berkeley), you must consult with your Engineering Student Services (ESS) Adviser before registering for the courses.
In general, students are not allowed to enroll at another school during a fall or spring semester while enrolled at UC Berkeley. Under very unusual circumstances, students have been given permission to enroll simultaneously. You should consult with your ESS Adviser to discuss simultaneous enrollment for your specific circumstances.