It makes the issue less black and white when a sizable chunk of those that benefit from AB-540, the instate tuition legislation, are American citizens.

From the Chronicle of Higher Education:

The University of California said it offered 1,639 exemptions under the tuition law in the 2006-7 academic year. Students classi?ed as “potential undocumented” immigrants received 271 of those. Most of the other exemptions went to students whose families had recently moved to California. Community colleges offered an estimated 19,300 exemptions, with about 90 percent of those believed to be undocumented immigrants.

Related issues, involving whether undocumented immigrants can attend public universities, have cropped up in Arkansas and North Carolina. The North Carolina community-college system recently banned undocumented immigrants from attending its institutions, while the Arkansas attorney general ruled last week that state and federal law did not prohibit undocumented immigrants from attending state institutions.