Bush no more enforces the immigration laws then Clinton did. The President does not enforce immigration law, he appoints people who will. His first appointment, Zigler, was a complete and under failure, Bonner is much better, but has to run things through Asa Hutchinson and Ridge, both idiots in my book.
No, apprehensions are down because of 9/11. Illegal aliens feared they would be thought of as terrorists. As that fear ebbs, the apprehensions will increase. 2004 will be that year.
Apprehensions are down because the INS work force was diverted by 911. Not because illegal immigration subsided. Illegal immigration is now above pre 911 levels. Bush's January 9 pronouncement opened the flood gates, albeit an uninformed basis from the standpoint of the immigrant.
Bush's announcement created such a rush that within 6 weeks Ridge had to shore up the border patrol to fight the flood.
Did Bush do anything worse than his father or Clinton prior to 911? No. But that's not an excuse for his behavior. Prior to 911 there were symptoms appearing all over the southwestern US that the flood of illegal aliens was sapping the state infrastructures and Bush did nothing.
Post 911 Bush's posture has simply been inexcusable. He has singlehandedly done more, either through implied invitation or inaction that any other US president to accelerate illegal immigration in just 3 short years.
Other than the politically motivated raid on WalMart, there have been no "residential roundups", the most effective tool in our immigration arsenal, since 1987. This is the first program I would have expected a conservative president to reinstate post 911 if for nothing more than its domestic public relations value.