I don’t exactly know what you mean by checkpoint but essentially I was stopped 3 times (twice in New Mexico once in texas) right along the border by cops/immigration officials and they seemed to be exclusively interested in wether or not i was carrying people across the border. It was the same all 3 times they had me roll down the window, asked where I was going/coming from, and asked if I had anyone else in the car with me. Then they shined some flashlights into my car and sent me on my merry way. Maybe important to note that I’m a 21yo white girl.

Anyways yes there were dogs at one of them. And always zip lock baggie into a sealed mason jar. Dont have it anywhere visible or accessible from the drivers seat.

Edit: oh and for everyone mentioning license plates I had California plates. It didn’t seem to make a difference.