Are you thinking about the red river? Border issue between TX and OK. Not sure but I think the BLM wanted to claim a wide swatch for the feds.
It’s a vague memory, so perhaps. However, I do remember it being related to a Land Grab by the BLM and I’m pretty sure the Rio Grande was mentioned.
I think the BLM was trying to make that case re Texas Oklahoma a legal precedent for additional taking along Rio Grande. However, as I said it was long ago, and very vague, so I may not be remembering it correctly at all.