Do Away with ICE?

I believe it was Noah Smith or Matt Yglesias who asked for a piece on whether we need a federal internal police force focused on immigration.

This is the way I'd analyze it:

Question:  do we want federal laws on immigration or not?

Answer: if we do, then you have to deal with the situation where people violate the laws and are inside the U.S.

Options: 

1. Have the laws but don't enforce them (similar to laws on prostitution, speeding, etc.)--not acceptable to public opinion now, though it might work in a less frenetic environment.
2. Have state and local police enforce the laws--as long as immigrant is a fraught issue probably not a good option because you'd have great variation in enforcement (i.e., sanctuary cities) 
3. Have the FBI or other existing federal police body enforce the laws.  This would shake things up, but in the long run the causes that ICE may have developed into an organization with a culture and standard operating procedures some, like liberals, find offensive likely would recreate the same problems.  (IMHO, any situation where there's power on one side and no power on the other is very likely to devolve into something bad--"power corrupts, etc."
4. Reorganize ICE under new authorities and new leadership.  That's what will happen if the Dems win in 2020.