Bank guarantee is one of the important international trade means which is issued to attract trust of purchaser (beneficiary), and to guarantee seller’ s obligations. If the seller violates its obligations, purchaser will demand the amount of guarantee. Bank guarantees, basically, are issued in such a way that are payable with beneficiary’ s first demand. In some cases, however, because of multilateral or unilateral sanctions, beneficiary could not be paid; this is frequently experienced by Iranian banks and traders. These sanctions based on their source that it would be an international organization or a state, would have different effects on guarantees. Sometimes sanctions have direct effect on guarantees and sometimes it would related to basic contract, and this raises this question that, does the law which put sanction on basic contract extent to guarantees? This paper shows that multilateral and unilateral sanctions have different scope to enforce, and base on this condition they would prevent the payment of guarantees. Base on sanctions regulations and their nature, they also would limit extension of guarantees even if they are only related to basic contract.