It’s illegal for a country to annex a part of another country by making a deal with a part of that country. Somalias dispute is with Ethiopia and it will win at ICJ and other international forums like the security council. The 1960 nonsense is not a thing.
In addition to all of this, Somalia’s arms embargo has been lifted and it would be well within international law to go into that region and enforce its laws. The arms embargo only lets the federal government import weapons.
You need to learn basic defintions. Like what annexation means.
The ICJ is an option but Somalia is scared for reasons you know and we don't have to get into.
Somalia isn't going to war for obvious reasons too. Are you finished yet?