venting tub under slab into p trap?

Im in AR and I had a plumber ask me if it were now legal to vent the tub drain into the p trap under slab. I need a little help on this one.

The question makes no sense. You NEVER vent a tub, and ALWAYS vent the "P" trap. There would be no way, or need, to "vent the tub into the P trap", under the slab or anywhere else. I doubt that he is a "real" plumber if he had to ask that question.