Theoretically, it is possible with a lot of skill and suitable tools such as fine whetstones or fine diamond files, but there is a risk that the geometry of the cutting edge will be changed, which can impair the cutting behaviour.
In addition, by reworking the cutting edges, the reach of the pliers becomes narrower, because the hardened cutting area is “worn away” and becomes ever thinner.
If resharpening by machine grinding, the hardness may be reduced by the introduction of heat during grinding. The time, effort and risks of re-sharpening are huge, so it is usually not worth it.