Yes, unless restricted by contract (such as with a union), there are no assurances of continued employment, on any basis. If the only jobs now available are per diem, there is nothing unlawful about that, as long as the selection process is not done on a discriminatory basis.
They say you get what you pay for, and this response is free, so take it for what it is worth. This is my opinion based on very limited information. My opinion should not be taken as legal advice. For true advice, we would require a confidential consultation where I would ask you questions and get your complete story. This is a public forum, so remember, nothing here is confidential. Nor am I your attorney. I do not know who you are and you have not hired me to provide any legal service. To do so would require us to meet and sign written retainer agreement. My responses are intended for general information only.
Mr. Kirschbaum is absolutely correct. Employees have very few employment rights, and employers have a lot of leeway in how they choose to run their businesses. Please see my guide to at-will employment in California which should help you understand your rights now and in the future: http://www.avvo.com/legal-guides/ugc/a-short-summary-of-california-at-will-employment.
*** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***
At-will employment means just that: either you or the employer can choose to terminate the relationship without consequence.
You are at-will unless you have an employment contract either individually or through a union.
Notwithstanding the above, an employer may not take adverse action against you based upon your race, religion, gender, sexual orientation, etc. (there are other protected categories as well). However, if they have simply made a business decision to eliminate full time positions they have the right to do this.
This answer does not create an attorney/client relationship and is provided for general information only.