[acadapter]

It's not a situation where someone is "giving up land". Croatia doesn't claim the land from its own legal perspective. The Croatian ambition is to use a historical path of the Danube river (from something like ~150 years ago) as the border. This way, Croatia could control larger pieces of land which today belong to Serbia. The line of control, after the war, is the modern-day river, which follows Serbia's claim.

However, despite Croatia's claims, there's also been some gray-area Croatian forestry going on there, through Hrvatske Šume. And since the Liberland movement started to claim the parcel as "no man's land", Croatia started patrolling it with police and arresting people occasionally.