Belhar was proposed to the presbyteries. It hasn't been added yet. However based on votes so far I'd say it will be approved.
I don't object to it. The main argument I saw against it was the the Confession of 1967 covered the same issues better. The main argument for it is that it's being accepted by other Reformed groups, and thus is a reasonable candidate for a confession of the whole Reformed community.
Here's the text:
https://www.rca.org/resources/confession-belhar. I don't see that it proposes any particular political policies, socialist or otherwise. The social teachings it does mention are directly from the Bible.
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Saying that the latest standard is Westminster is accurate for the conservative Presbyterian bodies. The PCUSA accepts the following later standards:
* Barmen
* The Confession of 1967
* The Brief Statement of the Reformed Faith
* [if adopted] Belhar
It also accepts several 16th Cent confessions. Presbyman says that this addition tends to weaken the confessions. I believe it was the intention of the change to show that many in the PCUSA do not agree with everything in Westminster. It surely should not be a surprise to readers here that many in the PCUSA do not agree with Westminster on a number of important issues. I believe it's good that our published standards reflect our actual teachings.