Due to many nations having limited sized cities, and oftentimes a small amount of actual territory to build in, dereliction policies are a must. Similar to a landlord evicting a tenant, if a building remains in a nation unused or empty for too long the leadership of the nation or owners of the property may choose to derelict the property. There is rarely a willing dereliction, however, and in larger or more complex builds it might take a few days or weeks to fully break all the reinforcements and empty out the plot.
Some nations like Yoahtl have a fairly strict dereliction policy due to the self imposed small city sizes and its often up to the dereliction officer to mark properties for dereliction. If a property owner goes several weeks without logging in, for example, a sign may be posted outside of the property informing the owner of dereliction. If no protests are made, then the property is derelicted and the valuables moved to the dereliction room. There was once a policy to post on discord when a property was marked for dereliction, but it was soon revealed to be counterproductive as players who would neglect to log in for weeks would log in for an hour or so to avoid losing their property.
Other nations like Mt. Augusta place a lot more power into the hands of property owners. The process of derelicting a house or property is very complex and often results in lawsuits and protests.