If a company decides to change that then you must agree to the new contract, or they risk legal action. If you don't then their options are keep you where you are or fire you, and of course firing someone is it's own minefield, as shown here.
Most places, work happens at the whim of the employer (and, for what little it’s worth, the whim of the employee): employment is “at-will,” states are “right-to-work,” and so on.
Don’t know about others, but I’ve never once in my life signed a contract to work in the US.
In most cases employment in the US is at-will and does not involve a formal employment contract: https://en.m.wikipedia.org/wiki/At-will_employment
If paid hourly, you're typically entitled to 1.5x pay after 40 hours of work. Salaried exempt status are not mandated overtime pay.
What hours you work depends. Salaried is expecting a job to be done regardless of the hours to complete. Hourly is a mixed bag of "the schedule for next week is posted every Tuesday" (common in restaurants) or routine hours long-term (such as shift work in factories).
It's awkward to try to explain, but here are some pros and cons from other people. https://www.reddit.com/r/RedditForGrownups/comments/16606tt/...
https://europa.eu/youreurope/business/human-resources/employ...
>When you hire staff, you should provide them with a written contract or an equivalent written statement confirming their working conditions
The fact it can be a statement rather than a contract may have an impact on the companies ability to change it at any given time without agreement from the employee, but I'm not an EU employment lawyer
When covid started, my company gave all employees annexes to reduce our pay by 20%, but keep our workload the same. I told 2 bosses, the HR employee and the director of HR mobbing me I will not sign and to piss off. I was the only one to do so out of ~150 employees. I kept my full salary until I quit my job because I don't like working for cunts.
In my country, which is in the EU, having someone work for you without a contract is a crime. Because by not having a contract you're denying them rights such as pension contribution, paid vacation, health insurance etc.
Plus you have to pay taxes on salary, so if you hire them "on a handshake" as it were, you're probably doing tax evasion too.
I've seen constructive dismissal discussed for even adding on-call to someone who was hired without on-call requirements, unilaterally. The logic being "You're suddenly asking me to be paged at any time when on call, that wasn't part of the job description", and it is paramount to effectively "firing and re-hiring" a person in another role without their permission.
Why I mention legal jurisdictions, and the above example, is because some US states are 'at will' employment states. In such a state, you can just fire anyone at any time, and thus the whole "fired and re-hired" thing doesn't kick in... as the 'fire' part is a-ok.
People have contracts in such states, typically, especially at a CPO executive level. So I really wonder here, will this be more about breach of contract?
(Of course, there are other issues. The disclosure of medical info... that's just bizarre, and smacks of massive inexperience and lack of judgement, if true)