What is the law regarding a foreigner in Venice?

Portia tells Shylock to remain in the court. She says that Venice has a further law which says that if any foreigner tries to kill a Venetian, the foreigner will have half of his property go to the Venetian against whom he plotted, and the state will receive the other half. In addition, the life of the foreigner will be in the hands of the Duke, who may decide to do whatever he wants to. Shylock is forced to kneel on the ground before the court, but the Duke pardons his life before he can beg for mercy.