There is no express provision under the applicable Mexican law providing that a copy of an attorney-client communication held by the client is also protected. The professional secrecy obligation applies only to the lawyer. It is commonly a matter of agreement between the parties that any information that the lawyer, in the strict exercise of their profession, provides to the client should be kept confidential.

Both in civil and criminal matters, Mexican law regulates who has the obligation to maintain professional secrecy, in order to protect fundamental rights to intimacy, defense, privacy and the inviolability of communications.

There is a general obligation for third parties to assist the courts in finding out the truth, with the exception of precisely those obliged to maintain professional secrecy (in addition to direct relatives in the vertical line and spouses).

When a client is facing criminal proceedings, the privilege of the secrecy of communications between lawyer and client consists in the fact that the lawyer has a duty to preserve the confidentiality of information and documents referred to by the client, in order to be in a position to produce their defense, and they are therefore exempt from the obligation to inform the authorities of facts that could be related to the commission of an illegal act. Therefore, the information in the lawyer's possession is considered confidential information, in terms of the General Law of Transparency and Access to Public Information.

The exception to this rule is that the privilege of confidentiality does not operate when there are indications that may implicate the lawyer, not as a defense attorney, but as a co-participant in an unlawful act.

Mexican law does not make any distinction between in-house or external lawyers with respect to privilege.

However, even though in principle both should be treated equally for such purposes, a court or administrative authority seeking the requested information might take the view that the relationship between an in-house lawyer and their employer client is based on an employment agreement and is not an attorney-client relationship. If that view is taken, the court or administrative authority may seek to compel an in-house lawyer to produce the requested information. The question of whether privilege exists will depend on a judge's decision on the specific facts of the case.

In order to minimize the risk of having to produce evidence, our recommendation for in-house lawyers is to enter into a nondisclosure agreement with their employer (i.e., client) that contains confidentiality clauses protecting any information the employer has provided.

Mexican law does not make a distinction between in-house lawyers and external lawyers. However, it can be assumed that in-house lawyers will be obliged to keep their employer clients' matters confidential only to the extent that such information was entrusted to them as attorneys and not as mere employees of the company; therefore, internal communications that do not relate to their employer clients' matters would not be subject to privilege.

As a general rule, foreign lawyers are not allowed to practice law in Mexico and therefore cannot invoke privilege under the professional secrecy concept. However, there are some international treaties that allow foreign lawyers to practice in Mexico under some conditions. In this case, they would be able to invoke privilege, as they would be subject to Mexican Law.

The Federal Law of Professions provides that all professionals, not only legal professionals, are obliged to preserve the secrecy of the information provided by their clients, with the exception of reports that are required by any applicable laws.

Certain people (doctors, lawyers, financial institutions, accountants, priests, among others) are obliged to maintain professional secrecy, and cannot disclose information obtained in the exercise of their professional activities, with respect to others. This obligation is effective against third parties and authorities, since they are required to respect the duty of confidentiality.