Arms embargo is a sanctions tool prohibiting the export of weapons to states or non-state actors that violate international law. It is one of the most popular tools employed by the Security Council and can be accompanied by other targeted sanctions, such as asset freezes, travel bans, financial sanctions and commodity interdiction. Stand-alone arms embargoes are rarely effective. They must be accompanied by other measures that limit financing, penalize influential players and restrict trade.

The success of a weapons embargo depends on the degree to which the embargoed state is dependent on a specific supplier. Import dependence is particularly dangerous for military and militia forces, which often build strategies and training programs around particular combinations of weapons systems. This can create a lock-in effect, requiring the importer to return to a particular supplier for ordnance, maintenance and spare parts. This supply dependency exacerbates the vulnerability of militaries to power asymmetry. It also undermines the ability of embargoed actors to diversify their arms acquisition channels and increase their risk-taking.

It is also a challenge to ensure that the prohibitions on exporting arms are actually enforced. Many charter aircraft and cargo firms have been used repeatedly to break UN arms embargoes. The UN Sanctions Committees and the Secretariat do not receive adequate support to improve their verification methods, techniques and procedures.

The effectiveness of an arms embargo depends on its ability to prevent the transfer of SALW (small arms and light weapons, such as pistols or assault rifles) to illicit or illegal markets. Such transfers are often facilitated by state-sanctioned illicit trade and involve the complicity of officials at various levels of government. The proliferation of these weapons is harmful to peace and security, as they increase the likelihood of chaotic warfare, and can amplify violence, including against civilians.