Simplify the following text for a Grade 13 native English-speaking person.
Original: A single member of parliament 's belief that a measure was injurious to his own constituency ( usually simply his own estate ) , even after the act had already been approved , became sufficient to strike the act .
Simplified: A single MP 's belief that a measure was injurious to his own constituency ( usually simply his own estate ) , even after the act had already been approved , became sufficient to strike the act .