A possible explanation for why there is currently more interest in controlling the influx of illegal workers is that some people really are concerned that persons with malicious intent could easily hide themselves among those who enter by ways other than legal tourist or immigrant channels.

As a consequence of that concern it is my understanding that it will require a passport to enter the US from either Mexico or Canada in the near future. That includes US citizens travelling to either country. They will have free passage out of the US (assuming no new rules by Canada or Mexico) but will be required to show a passport to re-enter the US. (Some congestion at ports of entry are anticipated?)

The likely effectiveness of this new law can be debated, but it obviously will have little effect on any potential "terrorists" if all they have to do is walk across the Mexican border amid another 200,000 covert arrivals. (Although at the favored crossings, it's often a 100 mile walk in brutal desert conditions.)

John