I wouldn't use "UK" to describe the Gibraltar border, because territories of the UK do not form part of the UK (see the first sentence here). I presume France/Netherlands refers to the St Martin/Sint Maarten border, which would work as long as you are using "Netherlands" to describe the Kingdom of the Netherlands, not the country of the Netherlands - there is a difference!
But it's definitely wrong to use Gibraltar since it isn't a country at all. It is, instead a part of the U.K., in the same way Greenland is part of Denmark or Saint Martin is part of Netherlands/France. That's why the asterisk ought to be there.
They supposedly share a 100-meter land border across a sand bank between them, but according to a handy google maps tool that plots the borders between countries the India-Sri Lanka border passes just off the coast of said sand bank.