I mean that's kinda like asking a future surgeon if they have any experience with operations and prescribing medicine. I've read dry, detailed material before, sure.
A future surgeon wouldn't have any experience doing surgery, no, but they can still have related experience. To be a surgeon, you have to have good hand coordination, attention to detail, and tolerance for long, tedious tasks. You also have to be able to remain calm under pressure and tolerate the sight of blood and hideous wounds. Just your life experiences alone should tell you how well you tolerate the sight of blood, how well you can handle working under pressure, and whether you have the coordination and attention to detail and tolerance for long, tedious tasks.
If you were considering a medical career, it would be wise to volunteer at a hospital--that would tell you if you could really stand caring for sick people. Or, you could become an EMT--that takes just a semester-long class, typically offered at community colleges, and then you start working on an ambulance. That right there would show you if you can handle medical emergencies, and if you really wanted to go to medical school, you could eventually, and your EMT experience would be the kind of work experience they like to see.
You're not considering a medical career, so that doesn't apply, but there are things you can do to get a feel for the fields you're considering. Psychology in particular can be tried out through volunteering--the kind of work psychologists do is often used by non-profit organizations, and they always need volunteers. You can't do the work of a fully qualified psychologist when you're not one, but you can do things in that ballpark. Suicide intervention hotlines, for instance, are staffed by volunteers, and they give you training before putting you out there.
There are also non-profit organizations in the law field, helping out people who can't afford the usual legal fees, doing lots of social justice work. It may not be the same thing as corporate law, but it would provide some sense of what a law career really entails.
Negotiated? No. But I imagine I'll be taught that if I go to law school, I don't think most people just simply have these experiences, you do learn them. (I hope that doesn't sound snappy, it isn't supposed to.)
Law school is mostly academic. So is grad school for psychology. That's a big failure of higher education, IMO: they don't provide the real world experience that you need in order to actually be able to do the job, or even to find out if that job is really right for you. At least, not until the last year or so.
And people do have those experiences in their lives. People who want to be psychologists often get an inkling they'd be good at it when others confide in them on a regular basis. Or else they have lots of experience being therapy clients themselves. In fact, when I took a counseling psychology course as part of my rather eclectic degree plan, one of the requirements was that we all had to have at least one appointment with the college counselor. If you had a problem to work on, it could be about that, and if not, it could just be personal growth counseling, and the professor didn't need to know any details, just that we had that one appointment.
Negotiating is also a life experience. People negotiate with their parents over what they're allowed to do (ie go out for ice cream or stay out later), with their friends over what to do together, with their siblings over who gets to play with what toy or who gets to sit by the window in the car or all kinds of other things that you have to share, with employers over scheduling and pay. You mentioned in another thread that you care for your niece and nephew. Surely you negotiate with their parents over when you take them, what you do with them, things like that.
I do actually want to call some people and ask questions, I've been thinking about that. It might not be a bad idea.
Go for it!