When patch 4.3
releases in the near future, you will not be able to sell items that you purchase with valor points back to a vendor for a short period of time once the patch launches and the valor-to-justice point conversion happens. This restriction is being put in place to curb the practice of buying valor point gear, waiting for the conversion from valor points to justice points, and then selling back the items for valor points. The last time the point conversion happened in patch 4.2, Blizzard ran into this problem and players got around the valor point conversion.
One of the criticisms of the point conversion last patch was that Blizzard had not given ample notice to players detailing issues with the new PVP set gear and some botched conversions that happened early. It appears that this time, Blizzard is getting ahead of the patch by a wide margin, letting players know about these new policies and procedures much earlier, so no one should be surprised when it happens. Early information is always welcome information. Check out the full item sell-back policy for the patch 4.3 point conversion in the blue post after the jump.