The Bush Administration has not been able to convince Congress to go along with its proposed liberalization of immigration.
So what to do? If they can't get new laws to do what they want to do, well, heck, they are going to reinterpret what current laws say so they can do what they want to do anyway.[The Borjas Blog: Immigration Policy]
The story he's linking to is U.S. lets in more immigrants for farms.[By Mark Boster , Los Angeles Times, October 7, 2007]
Officials at the three federal agencies are scrutinizing the regulations to see whether they can adjust the farmworker program, an unwieldy system used by less than 2% of American farms to bring in foreign workers. They are considering a series of changes, including lengthening the time workers can stay, expanding the types of work they can do, simplifying how their applications are processed, and redefining terms such as "temporary."
And it highlights a Separation of Powers problem—Congress can pass whatever laws it wants, but if the Executive Branch refuses to enforce them, the invasion continues.
The reason that farmers aren't using the farmworker program isn't that it's "unwieldy," but that it makes the farmer responsible for getting the workers into the country, and then out of the country, and housing them in between.
It's much more convenient for the farmer if he can just hire from a group of illegals wandering around in America, living in colonias near his farm.
That way, any extra expenses incurred by the workers, (such as medical care, a big item) will be entirely the responsibility of the taxpayer.