So 'which' one is it
Lord knows enough ink has been spilled on the that-which distinction and whether it matters much anymore.
But there are times when the distinction, aided by some inept editing, does make a difference as seen in this passage from an L.A. Times story in The (Columbia, S.C.) State:
The Presbyterian Church (U.S.A.) has been grappling with the issue of homosexuality for nearly 40 years.But the wording, "the assembly voted to repeal
The General Assembly meets every two years. In July, the assembly voted to repeal that requirement, which effectively blocks the ordination of openly gay ministers. Now the denomination's 173 regions, or presbyteries, have two years to vote on whether to ratify that change.
There's a hint in the next graf: The current balloting will be the fifth time efforts to ordain gay clergy have gone to such a vote. But your readers don't pay you for the thrill of solving a riddle.
Using "that" and no comma makes it clearer the clause refers to "requirement."
In July, the assembly voted to repeal that requirement that effectively blocks the ordination of openly gay ministers.