Hi all, I joined this forum last year planning a BIBE trip that unfortunately never happened, but still follow along here and hoping to make that trip soon.
Back then I had asked if alcohol stoves are legal in BIBE backcountry. Regulations seemed vague and even contradictory, phone calls to rangers were clear as mud. This new brochure seems to clear up the issue:
Campfires are not allowed in Big Bend National Park. In order to cook foods you may use a backpacking stove, portable fuel stove or the barbeque grills in your campsite.
(p.10 of the pdf, marked as p.3 of the brochure)
"Backpacking stove" and "portable fuel stove" certainly would seem to include alky.