I agree that it is probably an unlikely scenario to deport millions of illegals, but I do agree with the poster who advocated immediately deporting illegals who come into contact with ANY US law official.
It is unrealistic to think we could deport all illegals in the U.S. For one thing with the border open, they will simply return within hours or days. We could get the problem under control if we would do the following ASAP:
1. Secure the border
2. Cut off all social services for illegals (except true emergency items)
3. Crack down on illegal employment
4. Crack down on illegal documents and other things that enable illegals living in this country
5. Deport all illegals that come to the attention of LEO for any reason.
These steps should be implemented at the same time, and illegal immigration could be brought under control. Once we secured the border and began to enforce immigration laws many would return to their own country.