It isn't against the law for an illegal immigrant to enroll in a university; however, he won't be eligible for financial aid. What usually happens is that once a person is accepted into the university, the office sends him an I-20 form to have processed at the consulate office in his native country. This will help the student get a visa. However, if the student is already in the United States illegally, he isn't eligible for this visa. Depending on the school, you may or may not be able to attend. Call up schools that you are interested in and find out what their policy is. A lot of information is available on the Internet, or you can call the colleges' foreign-student offices. It would also be a good idea for you to consult a lawyer to clear up specific questions and protect yourself.