Ramesh sums it up well:

Nearly everyone in the immigration debate has claimed to favor enforcing the immigration laws. But if you think it is draconian to require that anyone have to show papers proving their legal status, then you’re simply against enforcement. And if you really believe that, you’re not going to change your mind just because the government has set up a ”temporary worker” program or a path to citizenship for illegal immigrants: You’re going to be against truly enforcing any conceivable set of immigration laws. Good to know.