You have to be admitted to the bar to practice law. Which is to say, other lawyers must recognize you as a lawyer, and this recognition can be taken away.
More practically, this means (in America) that you need a JD degree (4 year grad school), to pass an exam, and pass a(n oftrn horrifically thorough) character background check.
There is a difference between “legal counsel” or “legal representative in court”, with the former being less restricted (“has a law degree” vs “attorney/has passed the bar exam”)
Because of that, I think you can practice law without being admitted to the bar. Chances are it varies by jurisdiction, though.
It is my understanding that they must be certified. You are allowed to represent yourself, but it is my understanding that a non-lawyer cannot represent you.