If there were no other load on the supply, you would be correct. Most positive regulators can't sink current. A battery should work OK.Do let us know what is the outcome of this enquiry.
But a side question, the clamp(series R+ESD diodes) only works if there is load drawing some current on the VCC line. Now these uC can all go to SLEEP and consumes less a uA or less current drawn from the VCC bus.
Would forming a clamp with a high series resistor have the possibilities of raising the VCC potential over the allowable limit of the chip?