Joint locks legal on arms; some on legs (varies by belt + age); Chokes legal at Senior level; No heel hooks, no twisters, no neck cranks (more restrictive than ADCC or modern no-gi grappling)
Why people argue about this
People often assume that joint locks are automatically illegal in Jiu-Jitsu Ne-Waza just because they're called submissions. But actually, the key is which moves are specifically prohibited; some joint locks are allowed under certain conditions, leading to much debate and misunderstanding among competitors and spectators alike.