Assistance may be refused by both countries (depending on the terms of the agreement) for political or security reasons, or if the offence in question is not also punishable in both countries. Some contracts may help nationals of other countries to benefit from legal aid. For example, the Convention on Official Administrative Assistance in Tax Matters is a convention that facilitates the conclusion of bilateral agreements for the exchange of tax information between more than 90 States Parties. The EA Multilateral Agreement is an agreement signed among EA members, in which signatories recognize and accept the equivalence of accreditation systems managed by signatory members and the reliability of compliance assessment results accredited by signatory members. It makes the goal “Once accredited, accepted everywhere” effective. Modern states have developed mechanisms for requesting and obtaining evidence of criminal investigations and prosecutions. Where evidence or other forms of mutual legal assistance, such as testimony or the distribution of documents, are required by a foreign sovereign, States may attempt to cooperate informally through their respective police services or to resort to what are commonly referred to as “mutual assistance requests”.  The practice of mutual legal assistance has developed from the comity-based system of letters rogatory, although it is now much more common for states to directly address requests for mutual legal assistance to the designated central authority in each state. In current practice, such requests can continue to be made on the basis of reciprocity, but also under bilateral and multilateral agreements that require countries to provide assistance. A Mutual Legal Assistance Contract (MLAT) is an agreement between two or more countries to collect and exchange information, in order to enforce public law, including criminal law.
A rogatory commission is often used to formally question a suspect in criminal proceedings when the suspect resides in a foreign country.