AD - Layer effect border around external objects only

[Hewal]

Hello

Hello all. I've been trying for hours now to get it to draw a border around the outside elements only. 

But I can't get it to work. This is the initial situation:

 

If I now apply the layer effect Outline to the layer, it works very well, except for the 5 rectangles behind the cat. These are also outlined inside, but I don't want that.

If I drag out the group with the rectangles, the complete cat will have a black border. But it should only get a border on the left and right side of the pistols and on the tail. So everything "outside lines" so to speak. 

Do you have any idea how to do this?

Thanks for your help!
 

[GarryP]

The Outline Effect creates a raster outline around the non-transparent parts of the layer you are applying the effect to.
This means that the gaps in-between the rectangles – since they are transparent, there are no pixels there – will also have an outline applied within them, as you are seeing.
There are probably various methods to get what you want but the easiest might be to create a separate curve which contains the extents of the rectangles and then adding the Outline Effect to that while setting the Fill Opacity of the effect to 0%.
See my exaggerated attached image.
There will probably be other better methods.

[Hewal]

You mean I should trace the border with the pen tool and then put the effect on it? That's quite time-consuming (depending on the design). 
I have now packed everything into a group and then duplicated this group. Then I applied the Border effect to the group and rasterized it. I put the rasterized object into the background and used the eraser to free the corresponding areas. But this can also be very cumbersome. 
If anyone has any other ideas, feel free to share them