I think assuming that the CBP will adhere to the law is based on a pretty outdated mindset. I'd say at least since the current management, but more likely since 9/11...

I'd even call it a delusional mindset. For context, CBP and ICE were both formed in 2003. Jenn Budd has several books on this topic if you want to understand why a growing number of people want to abolish CBP, ICE, and even the entire DHS, which itself was formed only a year prior in 2002. These are very recent organizations in our nation's history, and if we're fine putting things like the Dpt of Education on the chopping block, why not DHS?