But it was false security. They were trusting in their own sufficiency. Trusting in the outward trappings of religion were not enough. Amos was saying much the same thing as Jeremiah said. There have always been those who trust in outward symbols of their religion, such as church membership or baptism or confirmation, or some other rite or ceremony.
Some people wear crosses, as if they have some magical power, and they feel secure.
But this is false security. Coming to church doesn't make you a Christian any more than standing in a garage makes you a car. If you are trusting in these outward things, beware. This is false security. You are only in the eye of the storm.