They patrol space. When their detector picks up an atomic explosion, they send a patrol.

10 seconds sound clip from the Dimension X - The Outer Limit by Graham Doar classic radio play.

You can hear this line at 00:17:19 in the radio play.

Quote context

[...]

- Where? How did I get in here? Who are you?

- Is he seeing things?

- Intergalactic Patrol? What's that?

- What are they saying, Steve? What are they saying?

- It's about nuclear fission - they know about it. They know the danger of it. Long ago they had wars that almost destroyed them. And finally they learned. Now they've outlawed war.

- Go on, Steve.

- They patrol space. When their detector picks up an atomic explosion, they send a patrol.

- What are they going to do?

- They've quarantined us!

- They've isolated the Earth, 'cause we don't know how to control ourselves yet. Until we learn, we'll be a menace to the whole universe!

- What is this nonsense?

- Quiet.

- How are they going to do it, Steve?

[...]