Bernie,

The pledge says "I will not . . ." it doesn't say that you can't sell them, just that if you do I won't do business with you.
There is a world of difference.

I am perfectly willing to let you make the economic decision of whether to sell slabbed chips OR sell chips to me.

I would rather have people come to a convention and watch the dealers selling slabs struggle, then have them come and not see any slabs. the first instance discourages others from selling slabs. The second only discourages selling slabs at the convention and in the magazine.