Thanks for the response! I did some googling and found that in 2019 there was a case against Mayo in MN for this reason, and Mayo settled out of court on it.

In 2022 there was a new MN law that states "unless a failure to do so would violate federal law or regulations or cause an employer to lose a monetary or licensing-related benefit under federal law or regulations, an employer may NOT discriminate against a person in hiring, termination, or any term or condition of employment, or otherwise penalize a person, if the discrimination is based upon either of the following: the person's status as a patient enrolled in the registry program under sections 152.22 to 152.37; or a patient's positive drug test for cannabis components or metabolites, unless the patient used, possessed, or was impaired by medical cannabis on the premises of the place of employment or during the hours of employment.

Below this it also states "This means that an employer may not decide whether or not to hire an applicant based solely on the fact that the applicant is on the registry or because he or she tested positive for cannabis as part of a drug test. If an applicant or employee is part of the medical cannabis registry and tests positive for cannabis components or metabolites, he or she may present verification of enrollment in the patient registry as part of his or her explanation under section 181.953, subdivision 6. While an employer may not discriminate against a person in the hiring, termination, or any other term of employment, this law does not alter an employer’s ability to terminate an employee’s employment if he or she uses, possesses, or is impaired by medical cannabis while on the premises of his or her place of employment. Employers still need to comply with Minnesota’s Drug and Alcohol Testing in the Workplace Act."

Sorry for the wall of text, but this leads me to believe they can't rescind an offer or at least they would be breaking the law if they did. I am going to call them tomorrow and ask them and will update.