"U.S. Customs and Border Protection (CBP) offices across the Nation work together with Federal, state, local and tribal law enforcement partners to achieve a unity of purpose and maximize operational integration, along with providing for the safety of the public and our law enforcement partners. These partnerships exist by sharing resources needed to address threats or emergencies.
Law enforcement agencies routinely request CBP assistance with enforcement activities for various reasons, such as officer safety. CBP is committed to promoting targeted and risk-based operations, and CBP will continue to assist other law enforcement organizations when practicable, as we have done historically.
If a Federal, state, or local law enforcement organization, other than another Department of Homeland Security (DHS) component, requests CBP assistance based solely on a need for language translation, absent any other circumstances, those requests should be referred to a list of available local and national translation services such as those provided by the Interagency Working Group on Limited English Proficiency. Nothing in this document should be construed to limit the authorities of an officer or agent when responding to other law enforcement requests for assistance.
DHS emphasizes the need for joint planning and actions across discrete elements of govermnent and society in order to promote public safety and ensure border security. When called upon to assist other law enforcement organizations, officers and agents are reminded to always act in a professional and responsible manner, and ensure that all enforcement actions are within the scope of our authorities.
This memorandum, which may be modified, superseded, or rescinded at any time without notice, is not intended to, does not, and may not be relied upon to create any right or benefit, substantive or procedural, enforceable at law by any party in any administrative, civil, or criminal matter." - CBP, Nov. 21, 2012. [Note: The official URL (link) to the CBP website may not open the PDF document in all browsers. For example, I can get it to open in Firefox, but not Chrome.]