Federation law is too complex, so complex that many lawyers will never practice in other states throughout their lives.
Because it is no longer just complicated, but constantly changing!
The Federation Congress proposes amendments to the Constitution and federal law every year, sometimes a few times, a dozen times, or dozens of times, changing back and forth.
If it were only this, it wouldn't be a big problem.
But state law is the same, undergoing many changes every year.
Take the state that prohibits standing while urinating at night, the regulation "no standing while urinating at night" has been modified many times.
Initially, it was only after eleven at night that urinating was not allowed, but they felt this was too inhumane, so they changed it to not making too much noise with splashing water while urinating.