One other issue which we discussed with the Professors was their opinion on whether Guatemala had annexed the Sarstoon.  It's been three years since the Guatemalan military has been behaving aggressively on the river that forms the southern boundary between the two countries.  And by aggressively we mean using the Belize sider of the river, and menacing - even detaining - Belizeans or the BDF when they traverse the Sarstoon.

The professors wouldn't call it annexation - per se - but said that it is a situation where going to the ICJ could help:…

That happened between Costa Rica and Nicaragua - where Costa Rica filed a request with the ICJ for interim measures on the Isla Calero.  That's a disputed island which the Nicaraguans occupied in 2010.  The ICJ got involved and ordered the area to be de-militarized:

In 2015, the ICJ ruled that the territory in dispute belongs to Costa Rica.