Express or implied agency
An agency may be expressly agreed upon or implied. It may be oral unless otherwise required by law to be in a specific form. Conversely, it is implied from: (a) the acts of the principal, or (b) his silence or his failure to repudiate the agency, in both cases the principal knows that another person is acting on his behalf without his authority.
Between those who were present or absent
Between persons who are present in the same place, the acceptance of the agency may also be implied if the principal delivers his power of attorney to the agent and the latter receives it without any objection. Between those who are absent, the acceptance of the agency cannot be implied from the silence of the agent, except: (a) when the principal transmits his power of attorney to the agent, who receives it without any objection, or (b) when the principal entrusts to him by letter or telegram a power of attorney with respect to the business in which he is habitually engaged as an agent, and he did not reply to the letter or telegram.
Notice via special information or public advertisement
If the principal specially informs another that the former has given a power of attorney to a third person, the latter becomes the duly authorized agent.
Best Legal Practices:
Publish in papers of general circulation the revocation of agency – As revocation of an agency depends on how third persons were notified, the manner previously observed in notifying a third party of the agency should be followed in the revocation as well. If a third person is given notice of the agency through a letter, another letter should be sent informing him of the revocation. The same goes for notice made by publication.
Publish in papers of general circulation the revocation of agency – For good measure, and even after a special notice of revocation, it is best to publish the revocation of the agency in papers of general circulation. The publishing of notices in such manner binds the whole world so to speak.
If the principal states by public advertisement that he has given a power of attorney to a third person, the latter becomes the duly authorized agent to any person or everyone. In both circumstances, the power of agency continues to be in full force until the notice is rescinded in the same manner in which it was given.”
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 CIVIL CODE. Paragraph 1, Article 1869.
 Ibid. Paragraph 2, Article 1869.
 Id at 5.
 CIVIL CODE. Article 1870.
 CIVIL CODE. Article 1871.
 Ibid. Article 1872.
 Ibid. Paragraph 1, Article 1873.
 CIVIL CODE. Paragraph 2, Article 1873.