The parts marked in bold are what I am unsure about in this sentence...
The dictionary entries of 「禁じ手」usually are limited to 'unallowed moves' or fouls in sports; however judging from this sentence I believe it can mean something like 'taboo' as well. Furthermore I was struggling with understanding 「扱いだして」but I think it means something like 'starting to sell/handle/etc.' here.
In short my questions are whether my understanding of above-mentioned is correct or not.