Can My Employer Legally Change My Job Code And Duties Without Notice, A Raise, Or Formal Hr Process?

--Can my employer legally change my job code and duties without notice, a raise, or formal HR process?**

Location: CA, USA

I've been working as a day shift Per Diem Critical Care Respiratory Therapist for 2 years under a specific job code — adults only (it's what was listed on the job posting online). I was hired under "Per Diem Critical Care Respiratory Therapist" and have never floated to the pediatric side, which I also declined when asked.

**Background:** The company has been restructuring and recently laid off ~20+ FT/PT respiratory therapists from both the adult and pediatric sides, leaving the pediatric hospital side chronically short-staffed, both days & nights. They've since received funding to open 20+ new per diem positions designed to float to both sides — and it now appears they're trying to quietly convert existing adult-only per diem staff into those roles without a formal process.

Today I showed up to work and was handed a paper with a **different job code** and told to read and sign it. No meeting, no HR, no explanation, no raise.

Here's a direct comparison of the two job codes:

**Current (4566):

Certifications: ACLS, BLS, PALS
Areas: ICU, CCU, Med/Surg/Oncology etc.
Service Age Population: Adolescent, Adult, Geriatric

**New (4564):

Certifications: ACLS, BLS, PALS, NRP
Areas: ICU, CCU, Med/Surg/Oncology, PICU, NICU
Service Age Population: Adolescent, Adult, Geriatric, NICU, PICU

So they are formally expanding my patient population to include neonates and PICU patients, and requiring a new certification (NRP) — all with zero compensation adjustment, zero formal training plan, and zero HR involvement.

I do have some PICU background (3 months orientation), but NICU, PICU, and peds in general are not areas I want to work in (outside the ED environment), and I have serious concerns about being thrown into those units without adequate orientation.

My questions:

1. Is it legal to unilaterally change an employee's job code, expand their scope of practice, and require new certifications — without a pay increase or formal process?
2. Is a 1-week deadline to sign a job change reasonable or even legal?
3. Should I go to HR before the deadline and request formal clarification in writing?
4. What happens to my original job code (4566) if I refuse to sign?
5. Given the recent layoffs and new per diem restructuring, does this look like a constructive dismissal situation?

The clock is ticking before the "1 week deadline". Any insight from HR professionals, RTs, labor law folks, or anyone who has navigated something similar would be hugely appreciated.