It is not the agreement but Somalia itself that will be declared null and void!
If it was a "break-away" already for over 30 years and you didn't undertake any measure to restore your sovereignty, then trying to portray this agreement as aggression, it simply shows how desparate you are.
https://www.trtworld.com/africa/somalia-ethiopia-somaliland-port-deal-null-and-void-16498297 wrote:Landlocked Ethiopia has signed an initial agreement with Somalia's breakaway region of Somaliland to use its Red Sea port of Berbera.