Don't Tread on the Bear!

 is an unmarked quest in Fallout: New Vegas.

Quick walkthrough
The NCR has a robust network of informants. If you continue to work with Yes Man/Mr. House, the NCR will no longer accept your help, or if you continue to help Caesar's Legion the NCR will brand you as a terrorist. This dummy quest will appear when you complete The House Always Wins, III or Wild Card: Side Bets. If you complete the next quest of the particular questline, it will say you have failed this quest and you will no longer be able to take on NCR quests. Any NCR quests active will immediately fail as well.

Behind The Scenes
Don't Tread on the Bear! is a reference to the "Gadsden Flag", a historical flag that depicted a coiled rattlesnake over the phrase "Don't Tread on Me."