蓝铅笔原则（blue pencil doctrine）是普通法系国家常用到的一个概念，它指的是在合同中存在冒犯性的词句〔offending words〕时，用以确定是整个合同无效还是仅该冒犯性的词句无效的一项司法准则。如果可以仅通过用蓝色铅笔划过该冒犯性的词句将其从合同中删除，使不合理的限制变得合理，则法庭应认定仅该冒犯性的词句无效，合同其余部分仍然有效并应予实施。

其英文释义如下：

The blue-pencil test is a judicial standard that the courts use to decide whether to invalidate the whole contract or only the offending words. If this standard applies, then only the offending words are invalidated if it would be possible to delete them simply by running a blue pencil through them, as opposed to changing, adding, or rearranging words.

然而，如今很多法院都已放弃了“蓝铅笔”原则，转而开始采用“合理性原则rule of reasonableness”来判定协议合理与否：

The rule of "reasonableness" permits courts to determine, on the basis of all available evidence, what restrictions would be reasonable between the parties. The ‘reasonableness’ test differs from the "blue pencil" test only in the manner of modification allowed. It permits courts to fashion a contract reasonable between the parties, in accord with their intention at the time of contracting, and enables them to evaluate all the factors comprising "reasonableness" in the context of employee covenants.

比如，当一份竞业禁止协议被判定为不合理时，包括全部不合理或者部分不合理，法院有权只在其认为“合理”的限度内赋予其有效的执行效力。

以下为相关双语示例，供参考：

However, even in those states where the courts routinely blue-pencil non-compete agreements, employers should not rely on that procedure for several reasons:

然而，即使是在那些法院通常采用蓝铅笔原则判定竞业禁止协议的州，用人单位也并不应该依赖该程序，原因如下：

Blue-penciling is expensive as it can only be done after a lawsuit is filed;

蓝铅笔代价较高，因为它只能在提起诉讼后进行；

Blue-penciling is unpredictable because it is up to the judge assigned to the case what he or she considers to be reasonable;

蓝铅笔结果不可预测，因为要取决于安排审理案件的法官决定哪些内容合理哪些内容不合理。

Blue-penciling can result in an employer not being able to recover damages caused by a breach of a non-compete agreement that occurred prior to a court rewriting the agreement.

蓝铅笔可能会导致用人单位无法就在法院修改协议之前发生的竞业禁止协议违反行为获得损害赔偿。