A shareholder may waive his preemptive right. A waiver evidenced by a writing is irrevocable even though it is not supported by consideration.

公司的股东可以放弃其先买权。这一弃权必须是通过书面形式来证明，而且在事后不可撤回，即使没有对价。

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However, agencies are asking supply teachers to sign a contract - known as a Swedish Derogation - to waive this right in exchange for continuous employment or a minimum payment if work is not available.

BBC: Wales

Thanks in part to this kind of coercion, more than 90 percent of defendants waive their right to a jury trial.

FORBES: Aaron Swartz and the Corrupt Practice of Plea Bargaining

Mr. Gingrich's admission and the full committee's acceptance of his request to waive his right to a disciplinary hearing means that this hearing is not about Mr. Gingrich's guilt or innocence.

CNN: AllPolitics - Ethics Transcript