avoid 和 repeal二者都可以指“撤销、使无效”，二者的区别主要在于使用对象的不同：

avoid撤销的对象主要是合同、协议；如，avoid a contract 撤销合同

repeal是书面用词，其撤销的对象往往是指撤销立法机关通过的协议、 法案或法律等。 如，repeal a ruling 撤销裁定

例 If time allows, the party intending to declare the contract avoided must give reasonable notice to the other party in order to permit him to provide adequate assurance of his performance.

参考译文：如果时间允许，欲宣告合同无效的一方当事 人必须向另一方当事人发出合理的通知，使其可以对履行义务提供充分保证。

例 If, after the signing of this Agreement, the Chinese government either at the State, provincial, municipal or local level adopts any new law, regulation, decree or rule, amends or repeals any provision of any law, regulation, decree or rule, or adopts any different interpretation or method of implementation of any law, regulation, decree or rule, which contravenes this Agreement or which materially and adversely affects a party's economic benefit under this Agreement.

参考译文：如果本协议签署之后，中国国家、省、市或地方政府通过任何新的法律、法规、法令或条例，修改或废除任何法律、法规、法令或条例的任何条款，或对任何法律、法规、法令或条例给予不同的解释或采取不同的实施办法，导致与本协议相冲突，或对一方在本协议项下的经济利益造成实质性的不利影响。

例 The amendment or repeal of any resolution of the board which by its express terms is not so amendable or repeal able.

参考译文：修正或废除董事会的决议，而该决议的条款明文规定不能由委员会修正或废除。