I just found this summary of a book I haven't read on Google Book Search.

Ronald Reagan and the Politics of Immigration Reform

By Nicholas Laham

Laham argues that Ronald Reagan demonstrated gross ineptitude in his conduct of immigration policy. He failed to press for much-needed reforms in legal immigration while he supported the establishment of a fraud-ridden employer sanctions regime, which had no discernible effect in achieving its goal of stemming the flow of illegal immigration.

He failed to take the first step toward the establishment of a fraud-resistant worker verification system, which would enable the employer sanctions provisions of the Immigration Reform and Control Act (IRCA) to be effectively enforced. Additionally, he supported the amnesty provisions of IRCA, which granted permanent legal residence to 2.7 million often poorly educated, unskilled, and low-wage illegal aliens.

According to Laham, Reagan's failure to develop a sound and effective immigration policy was not due to the president's urge to satisfy the desires of special interests. Rather, the Reagan administration was crippled in its ability to design a sound and effective immigration policy by the lack of accurate and reliable information on this issue and by the president's own ideological hostility toward big government.

These factors impeded the ability of Congress to design an effective employer sanctions regime capable of stemming the flow of illegal immigration to the United States. This thorough and controversial analysis will be of particular interest to scholars, students, and researchers involved with American immigration studies, the presidency, and contemporary public policy.

I agree that the IRCA Amnesty of 1986 was a disaster, but I'm not sure how much of the fault was Reagan's. However much we may complain about Bush's amnesty advocacy, in the end, immigration policy is in the hands of Congress. Which is good, otherwise we'd have another amnesty.

Of course, any law that's made has to be enforced, while Congressmen have frequently stepped in to block enforcement, the President can "block" enforcement by just doing nothing.

I don't believe Reagan did that, but Bush has.