Short answer. He may withdraw, but not silently and not always for free. The Civil Code lets an agent withdraw by giving due notice to the principal, and makes him indemnify you for damage the withdrawal causes — unless continuing would have meant grave detriment to himself.
What the law says
The agent may withdraw from the agency by giving due notice to the principal. If the latter should suffer any damage by reason of the withdrawal, the agent must indemnify him therefor
Civil Code, Article 1928 — Agent's Withdrawal. Read the full provision →
Notice is the first thing to look for
An agency is not forced labour, so the law does not chain an agent to a job he no longer wants. What it does insist on is due notice to the principal. Notice is what lets you find a replacement, meet a deadline, or stop a transaction before it goes wrong, and it is the difference between an inconvenient exit and a damaging one. The Civil Code does not fix a number of days, because what is due depends on the work: a broker abandoning a sale two days before closing and an errand agent stepping back from a routine task are not in the same position. Where the agent simply went silent — stopped answering, never returned the documents — the notice requirement has not been met at all.
When the agent has to pay for what the exit cost you
If you suffer damage by reason of the withdrawal, the agent must indemnify you for it. Two words in that sentence do most of the work. Damage means actual loss you can show — a forfeited deposit, a penalty you incurred, fees paid twice to engage someone else — not the frustration of being let down. And by reason of means the loss must trace back to the withdrawal itself, not to a market that moved or a counterparty who changed its mind. So the practical task, if you want to recover, is documentary: keep the agency agreement, the last instructions you gave, the messages showing when and how he pulled out, and the receipts for what you had to spend afterwards.
The escape hatch, and its limits
The agent avoids indemnity if he based his withdrawal on the impossibility of continuing without grave detriment to himself. That is a real defence and a narrow one. It contemplates serious harm — illness, exposure to legal risk, a demand that he do something improper — not that the job turned out to be tedious, underpaid or larger than he expected. Note what this provision does not cover. It governs the agent's own withdrawal, not your right to revoke the agency, and it does not by itself invalidate what the agent already did while acting for you before quitting. Nor does it excuse him from rendering an account and returning your money, papers and property once the agency ends.