They are legit but they have an abysmal bar pass rate:http://en.wikipedia.org/wiki/California_Southern_University
If you don't plan to move to California in the future, forget it.
If you want an online MSLS - get one from one of many regionally accredited schools like - Kaplan University. Regional accreditation means it is a "real" degree just like Cal State etc., anything less than regional accreditation means you may have wasted your time and money on a piece of paper. It is unclear to me if Cal Southern is regionally accredited or not.
A MSLS is essentially a fancy paralegal degree. I am not sure why anyone would need a masters degree to be a paralegal but people do go for it. Absent work experience, an online MSLS would be hard sell in today's economy to an employer.