How can you remove pvc 1/2" tubing from compression fittings?

Nope. It's permanent. You have to cut off.

This is posted in lawn and garden so I'm wonedring the application. OVC is plumbing is generally glue but like KISS points out its permanent on plastic tubing much of the time. Is this really PVC or plastic tubing like in a garden sprayer.

You cut the tubing, it is "fixed" so to speak onto the tubing and will have to be cut off.