Don’t get to take it home with you though if that involves crossing international borders.

Not only arms, but also money was raised and sent back to fund IRA activities.

Sure… Not all Americans, but IRA funding and support was pretty widespread in places such as New York. (Not saying it’s not understandable why people with Irish heritage, or Americans in general would support the IRA, just that US support for them was a very helpful lifeline.)

Edit: also smuggling guns into a conflict zone to arm one side is quite substantial help.

Not be, mostly.

The population density in the Highlands and Isles is very low.