Unilateral sanctions are economic or trade restrictions imposed by a single country against another country, individual, or entity without the backing of an international organisation, such as the United Nations. These sanctions are typically implemented to address issues like human rights abuses, terrorism, or financial crime, aiming to isolate the target from the global economy or exert political pressure. 

Compliance-wise, unilateral sanctions pose significant challenges for businesses and financial institutions. Companies operating internationally must navigate complex regulatory landscapes, ensuring compliance with not only global sanctions but also unilateral ones, such as those imposed by the U.S. through the Office of Foreign Assets Control (OFAC). Non-compliance with these sanctions can lead to hefty fines, legal action, and reputational damage. Robust sanctions screening processes and diligent monitoring help financial institutions avoid engaging with sanctioned entities and mitigate the risk of facilitating illicit financial activities.