CAVEAT: US info only; this is a legacy of our really crap health care and social insurance scheme, varies by state, please research for yourself.
It actually depends on the facility. In most nursing homes, no guns, but that’s because most of the people in nursing homes (or skilled nursing facilities; same thing, different names) are eligible for guardianship/conservatorship, whether that’s happened officially or not. A SNF can set more thorough rules, including restricting access to guns, cars, meds. This is also true for memory care facilities. Basically, any place where the majority of residents/patients can be considered unable to make their own medical decisions can restrict guns. My personal rule of thumb for guns is twofold: insulin and sex between patients. If the facility is willing to take responsibility for a patient’s insulin, they will probably prohibit guns, because the ability to manage one’s insulin depends on the ability to calculate and plan. If they won’t take on insulin, they might allow guns. If patients are allowed to have sex with each other or their significant others, guns might be allowed. If sex is prohibited, guns probably are, too. Guns are part of the spectrum of agency and consent, and people who are too impaired to consent are not allowed to have guns.
Assisted living is more… nebulous. Technically, assisted living is an apartment with a month to month lease that includes fairly specific meal, personal care and social structure support but not significant medical/legal oversight. And it gets complicated. Quite a lot of assisted living residents should not make their own decisions, but they still can and are assumed legally capable of doing so. Assisted living doesn’t provide medical staff; nursing homes do. (Though assisted often contracts with specific care providers. Which is for the patients’ benefit, but also leaves room for so much corruption.) Assisted living will usually take responsibility for oral and transdermal meds, but not injectibles (which makes finding diabetic care tough). An assisted living can restrict guns in the facility, but if a patient brought one in and got evicted for it, I can see that becoming a 2A fight. Technically, if it’s not legal for a landlord to restrict an action, an assisted living can’t, either. They can, and do, strongly discourage, but it varies by state.
