heckler’s veto

heckler’s veto
 n.— «The late Harry Kalven Jr. of the University of Chicago Law School invented the phrase “heckler’s veto” to characterize Mr. Taffel’s position. One taking that position says to the would-be demonstrator: You must not march because if you do I will become violent.» —“About Nazi Marches and the ‘Heckler’s Veto’” by Staughton Lynd in Niles, Ohio New York Times Sept. 30, 1977. (source: Double-Tongued Dictionary)