Is this in violation of any work laws or ethics?

it is called at will employment and you can be let go for any reason or no reason, saying no is any reason, not illegal

At will employment means the employer can terminate you with or without notice, as long as the reason for terminating you is not illegal. Meaning - sex, race, religion, etc...

In answer to your second question - reduction of hours, no this is not against the law to reduce someones work hours, for any reason. You can apply for unemployment based on reduction of hours, and possibly receive partial benefits, depends on how much you earn in the hours you are working.

They can legally fire you if you refuse to come in on 1 hour notice, but that wouldn't likely disqualify you for unemployment.

If an employer drastically reduces hours, you might be eligible for partial unemployment.

Unless you are a civil service government worker, a union worker, or a contract employee, your employer may fire you for no reason & any reasons. They may also cut your hours as much they want unless one of those categories apply. The only other exception is firing or cutting back because of unconstitutional discrimination - i.e., that which is based on race, creed, gender, age.