US v Emmons did not allow unions to use extortion and violence in their collective bargaining efforts.The issue at hand in that case was whether or not the Union was in violation of the Hobbs act of 1934,which prohibited extortion and robbery as a means of coercion of Union Locals
The ruling held that there was not a violation because the Local in essence,is the property of the Union,therefore the Union was not violating the extortion or robbery clauses of Hobbs.This is not to say that other violations didn't occur,just that Hobbs was not violated.
In the Buffalo case you cited,US v Emmons would not apply because the victims were not union members,but third parties who were being pressured to join the Local. The prosecutors in this case are not violating any legal or ethical standards because Hobbs doesn't apply to the extortion of independent individuals.
I agree that there is bad law here,but in my opinion, the bad law is in not overturning US v Emmons.
You have laid out the prosicutions case, I happen to disagree(again, I am not a lawyer to it is just my laymans observation)
My understanding of Emmons is that it makes no differnce is the "victims" are union members or not, and it's not that they can't be charged with a crime, it's just not "extrortion"
My issue is here anytime an emmo9ns defence is used, the Feds are going to cite this case as an exception.