citizen's arrest

昨天美國前總統布希到加拿大演講，入場費1400加幣。
場外卻比場內更熱鬧，抗議的群眾有好幾百人。
有人就說應該進行citizen's arrest。
到底是什麼意思呢?

An arrest made by a citizen, for whom legal authority arises from the fact of citizenship, rather than by an officer of the law.