Asking a bunch of strangers this very important question definitely seems like the best course of action. 

Hey its_aya_01.  I'm not sure if this response is moot, but I'm a lawyer trying to pivot practice areas (or careers), so I just started re-lurking on Archinect.  Maybe, I can help you...

However, I am a bit confused because in the United States, you can only get your law degree after obtaining an undergraduate degree.  

So, I guess there are two scenarios:

(1) You're in undergrad - so, what matters is what is required of your specific college/uni to graduate re: required coursework/core courses, electives, and major/minor courses.  If you want to study law studies in undergrad, you're free to, and I'm sure a certain number of your arch classes will credit towards your electives (or even perhaps certain core req's like visual arts/design.) You definitely need to ask your advisor/counselor assigned to you to make sure what courses you need to take to switch majors and graduate.  Definitely do not try and figure this out on your own.

(2) You're in grad school - then, ya, none of the coursework could be credited (unless you took a course that was e.g., land use law and was afforded credit to both the arch and law schools.  Highly unlikely...). So, if you want to switch grad programs, you'd have to quit architecture school and then apply separately to law school (and take the LSAT etc.)