Is there a way to lock rendered layers? Is it possible to lock which layers get used in compositing?



It get annoying having to re enable all the layers you want to use in the compositor every time you disable a bunch of layers to check just one or two layers to see what is on them.

Is this possible? If not, is there an easier way to check the contents of layers?
No, you can't lock a scene's layer visibility. To check layer contents, what I usually do is to reserve a separate 3D View area with its own active camera and layer visibility. 

You can have a 3D View area's camera and layer visibility settings detached from the scene's by toggling off its Lock Camera and Layers button, located to the right of layer buttons: