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.

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.

But the wording, "the assembly voted to repeal fthat requirement, which effectively blocks ...," is likely to make some readers come up a bit lame. Written, with the comma, it's easy to read the sentence so that the the relative clause applies to the entire concept of the vote - meaning the vote to repeal actually has effectively blocked ordination.

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.

 Making it "that had effectively blocked" makes things even clearer, but in this case it might not be so correct. Remember, there are two years to ratify the change, so the wording has not been officially repealed yet. I don't know enough to say, so I'm playing it cautious.

It wasn't a problem in the LAT original.