This question is inspired by the recent event of Grace 1 being detained by Gibraltar. Interestingly the most aggrieved party (which may or may not have legal standing though), namely Iran, has signed UNCLOS (in 1982) but not ratified it since then.
UNCLOS provides an arbitration procedure (ITLOS) that has been used for detained vessels and/or ship personnel in the past. (The EU, Italy actually, was involved in a case with India relatively recently. The Netherlands were involved in another case with Russia.)
So, I'm curious: may countries which are signatories but have not ratified UNCLOS use its arbitration procedure (ITLOS)? Are there any examples of that? Or (lacking that) more generally, are there examples of countries having signed but not ratified some other international convention(s) but which nevertheless have successfully used the arbitration provisions of said convention(s)?