Vision

The word for revelation here is: chazown which is translated a dream, revelation, or oracle; vision.  When the people have no prophetic vision to work from, restraint is cast off. 
The word for restraint is: para’ which is translated to expose,  dismiss, to make naked, to perish, to let loose, to show lack of restraint. 
When the people are operating from a place that lacks prophetic vision and direction from the Lord, they are like one who is exposed or naked, they show a lack of restraint and in that lack of restraint they perish. 

BUT……happy is he who keeps the law.
 In order to keep the law, one has to be familiar with the law.
 Spending time in the Word of God and in the Presence of God is the way to receive prophetic vision and direction. 

Having received that prophetic vision and direction allows for one to walk in a way that leads to restraint and life.