Looking at a DWI case with these facts:

Driver pulls onto the highway at 1 AM. Goes northbound in the southbound lanes, without headlights. BP agent sees this happen, and immediately makes a traffic stop and calls for DPS. Trooper gets to the location, takes over, does SFSTs, and makes the arrest (.19 PBT, but no blow at the station).

Defense counsel is arguing that the Border Patrol agent isn't a peace officer in Texas, had no authority to initiate a traffic stop, and has filed a suppression motion. His contention is that even if there was an dangerous situation, BP could not have defendant submit to a show of official authority without jurisdiction. Anyone have any starting points for research into this?

This should answer your question. Article 2.122(c) directly deals with border patrol officers.

Hope it helps, or at least give you a starting point.

Additionally, even if the defense attorney was correct about BP (as in border patrol, not the oil company), a citizen can make a citizen's arrest for a breach of the peace - and I would venture to guess that driving the wrong way down a highway would fall under that category.

To follow up on what Gretchen said, take a look at the annotations under CCP 14.01 to see what has been held to be a breach of the peace.

For example, driving on the wrong side of the road and forcing other drivers to take evasive action was held to be breach of peace. Ruiz v. State, 907 S.W.2d 600, Tex.App.-Corpus Christi,1995.