If a microchip can be implanted, it can be removed as well.
What’s that old saying? For every measure, there is a counter-measure.
The microchip should always be placed in the same location, if there is a scar at that spot, that would a red flag. Fingerprints, photographs and DNA swab could be taken at the same time as the chip placed, and if the red flag is raised, then the DNA, photographs, and fingerprints should be checked for. I think this could work. However, chips should be placed in everyone coming across the border. (This is mark of the beast stuff, isn’t it?)
Well how about this, if your chip is removed then you won’t be able to buy or sell anything! /s