Can private loan companies force repayment while the borrower is still in school?

A student loan was taken out, and deferment of repayment began immediately for a max deferment of 5 years before forced repayment. The borrower took time away from school and re-payed the loan while working away from school. The borrower returned to school, and is now being forced to repay as the max deferment has been reached. Is the private loan company allowed to do this? What rights does the borrower have? Where can I find information on student loan borrower rights and laws?