None of the 10 or so sites that sell this that I visited had anything about a ban, this may be a reason the sellers give to justify not carrying that product anymore. I have heard that type of excuse used before in place of the more honest that not enough people buy it to justify my giving it shelf space.

I just did a quick search, too, and Nature's Guide out of Fort Worth is still carrying it, as are other companies. Someone posted a query on here last year in the Organic Farming Forum asking where to get it. A kind responder linked them to the below article. The problem may be in companies selling it as an herbicide when it hasn't been cleared as such with the EPA. Buying plain ol' 20% vinegar shouldn't be a problem as long as it isn't labelled as being a weed killer. And a heads-up, the article's a .pdf.

Here is a link that might be useful: Acetic Acid Factsheet