Section 16603 sets out what happens the moment a partner is dissociated — the events causing dissociation being listed in § 16601, and including a partner's express will to withdraw, expulsion, death, bankruptcy and incapacity. Three consequences follow, and the second and third are the ones with commercial consequences.
First, the partner's right to participate in the management and conduct of the partnership business terminates. Leaving means leaving the running of the business; it does not by itself resolve the financial claim, which is governed by the buyout provisions where the partnership continues, or by winding up where it does not.
Second, the duty of loyalty under § 16404(b)(3) — the duty to refrain from competing with the partnership — terminates. This is the provision people are most often unaware of: a departed partner may compete with the firm they have just left, immediately, unless a valid contractual restraint says otherwise. Third, the duties of loyalty under § 16404(b)(1) and (2) — accounting for property, profits and benefits and appropriated opportunities, and not dealing adversely to the partnership — and the duty of care under § 16404(c) continue, but only with regard to matters arising and events occurring before the dissociation. So the former partner remains answerable for what they did while a partner, and is free as to what they do afterwards.
That division is the section's whole architecture: the past stays governed by fiduciary duty, the future does not. It also explains why the enforceability of a written non-compete matters so much on a partner's exit, and why the timing of an opportunity — before or after dissociation — is so often the contested fact. Both are questions to take to a lawyer.