Mutual legal assistance (MLA)

What is mutual legal assistance?

Mutual legal assistance (MLA) is a formal process through which public authorities in one country request legal or evidentiary assistance from authorities in another country for use in criminal proceedings or related investigations. In practice, MLA is used when evidence, assets, documents, witnesses, suspects, or procedural acts are located outside the state conducting the case, and those measures cannot be lawfully carried out without the involvement of the requested state.

MLA is based on national law, bilateral or multilateral treaties, and, in some cases, regional instruments that simplify cooperation between states. Depending on the legal basis, assistance may include obtaining bank records, hearing witnesses, serving procedural documents, searching premises, freezing or confiscating assets, transferring evidence, or identifying persons connected with an investigation. The exact scope of cooperation depends on the applicable treaty framework and the domestic law of the requested state.

Although MLA is closely associated with criminal matters, it is not limited to courtroom evidence alone. It often plays an important role at the pre-trial stage, especially in cases involving cross-border fraud, corruption, money laundering, tax offences, cybercrime, sanctions-related conduct, and offences committed through international corporate structures. In many cases, the success of an investigation depends on whether foreign authorities can legally obtain and transfer relevant material in a manner admissible under the requesting state’s procedural rules.

What does mutual legal assistance cover in practice?

In practical terms, MLA allows one state to ask another state to perform specific procedural acts that would otherwise remain outside its jurisdiction. A request may concern the collection of witness testimony, the production of corporate or financial records, the service of summonses, the execution of searches, or the restraint of assets. It may also involve requests to identify account holders, preserve electronic data, or obtain information held by regulatory bodies, law enforcement agencies, or other public institutions.

MLA is usually carried out through central authorities, prosecutors, courts, or other competent bodies designated under the relevant legal framework. The requested state generally examines whether the request meets formal requirements, falls within the available legal basis, and does not conflict with fundamental domestic principles such as sovereignty, public order, procedural guarantees, or restrictions related to political or military offences. In some systems, dual criminality may be required – meaning that the conduct under investigation must also be punishable in the requested state.

Different legal systems approach MLA in different ways. Some instruments allow broad cooperation unless a ground for refusal applies, while others define more narrowly which measures are available. There may also be differences regarding privilege, data protection, confidentiality, banking secrecy, ne bis in idem, limitation periods, or the standard of detail required in the request. For that reason, an MLA request that appears justified from the perspective of one jurisdiction may still be delayed, narrowed, or refused in another.

When is legal support important in MLA matters?

Legal support is important whenever criminal proceedings have an international element and authorities seek evidence or enforcement measures abroad, or when a person or company becomes affected by a foreign request executed in Poland or another jurisdiction. This may concern entrepreneurs, board members, compliance officers, financial institutions, witnesses, injured parties, and private individuals whose data, documents, assets, or testimony are sought through formal cross-border channels.

For businesses, MLA issues often arise unexpectedly – for example when a company receives a request to provide records, learns that a bank account has been frozen, discovers that foreign prosecutors are seeking information from a Polish authority, or faces parallel proceedings in more than one country. For individuals, MLA may become relevant when they are summoned for questioning, asked to produce documents, notified about the transfer of personal data, or exposed to asset restraint linked to a foreign investigation.

Early legal analysis can help determine whether the request has a proper legal basis, whether procedural safeguards were observed, what rights the affected party may exercise, and how cooperation with the authorities should be handled. A prompt consultation may also reduce the risk of procedural mistakes, inconsistent statements, unlawful disclosure of protected information, avoidable disputes with authorities, exposure to liability, or financial loss resulting from delayed action.

In some matters, legal assessment is especially important because MLA intersects with other areas of law, including extradition, data protection, internal investigations, regulatory duties, anti-money laundering controls, and the rights of defence. Where a company operates across borders, the same facts may trigger reporting obligations, employment issues, document preservation duties, and questions about legal privilege. Coordinating the response from the outset is often essential.

Law firm support in mutual legal assistance matters may include in particular:

analysis of MLA requests and the legal basis for cross-border cooperation,
representation in proceedings connected with the execution of foreign requests,
advice for individuals and companies asked to provide testimony, documents, or data,
assistance in matters involving freezing, seizure, or confiscation of assets,
coordination of defence strategy where proceedings involve more than one jurisdiction,
support in contacts with prosecutors, courts, and other competent authorities,
assessment of confidentiality, privilege, and data protection issues,
legal support related to corporate records, compliance materials, and internal investigations.

Need legal assistance in a mutual legal assistance matter? Contact us.

Mutual legal assistance (MLA)