NSL

NSL is an acronym with multiple meanings, of which the most widely known in a legal and security context is National Security Letter. In the United States, a National Security Letter is a form of administrative subpoena issued by federal agencies, principally the Federal Bureau of Investigation, to obtain certain records from third parties such as telecommunications providers, financial institutions, or internet service providers. An NSL allows the government to compel disclosure without a court warrant and is often accompanied by a nondisclosure directive that forbids the recipient from discussing the request.

Scope and limitations: NSLs typically cover metadata and other records related to a person or account, rather than the content of communications. They do not require probable cause or a full judicial warrant. Recipients are obligated to comply, though there are mechanisms to challenge the letter or certain aspects of its validity in court. The process has historically raised concerns about privacy and government secrecy, due in part to the secrecy typically imposed on both the letter and its existence.

Oversight and reform: NSLs originated during the post-9/11 security framework and have been subject to legal challenges, legislative debates, and reforms aimed at increasing transparency and limiting overreach. The USA Freedom Act and related developments addressed some data collection practices, but NSLs remain a tool under specific statutory authorities and are still in use for designated records requests.

Other uses: NSL can refer to other terms in different contexts, such as National Security Law in jurisdictions where a statute or set of laws is referred to by that name, or to other organizational or linguistic meanings in various languages. The specific meaning usually depends on the country and domain.