In a lot of areas in the US (but not all) a period of notice is necessary. This precludes events where a neighbor steals property from another surreptitiously.

In a lot of areas in the US (but not all) a period of notice is necessary. This precludes events where a neighbor steals property from another surreptitiously. In some cases if the land is "abandoned" you need to make the person who owns it aware of it, in others it is presumed if someone does not visit their land for 7 years they have no interest in it. (This is getting complicated and challenged due to the fact suburbs are popping up nearly everywhere and totally useless land may now be worth money.) In the case above simply demolish whatever the guy built. He tries to sue in civil court and fails because he had no right to build there.