Hero From Yesterday by Robert Silverberg - They were a peaceful people and somehow couldn't stand the thought of executing their only criminal. The answer was to discover a-Hero From Yesterday
The day Lugert's criminals gunned down three citizens in a bold broad-daylight robbery, Domnas Karson, Third Speaker of the Council, said, "I think I've got the answer."
"Answer? To what?" asked Murgon Darell Fourth Speaker.
"To Lugert," said Karson. "The weapon we can use against that throwback who's terrorizing us all."
Darell sighed wearily. "There is no answer to Lugert, I'm afraid. We're peaceful people; he's a throwback to a more violent age. There's no way to cope with him. Would you want to be the one to shoot him down?"
Karson shuddered and said, "No, not me. Of course not. I'm no more capable of violence than anyone else. But Lugert can be stopped. We can get help."
"From where?"
"From the past," said Karson. "From the ugly crime-ridden world we've evolved out of. Dr. Lorence of the Science Council has developed a time-net which...."
"Of course!" Darell exclaimed. "Bring a man out of the past! A man who won't be inhibited by our innate hatred of violence, a man who'll be able to deal with Lugert as he deserves!" He rose and strode around the long councilroom in quick, nervous steps. "Call Lorence, Karson. Get him at work on the project at once. We can't waste any more time. There's no telling when Lugert might...."
