He bought a piece of land, then he found out that it had been seized by force from public property

I put this question to our shaykh, ‘Abd ar-Rahman al-Barraak (may Allah preserve him), and he said:

If he bought it from him at the market price, then he does not have to do anything, but he should advise and exhort the one who seized it by force to give the money back to the public funds. If he bought it for less than the market price, then this purchaser must work out the difference and donate it to the public funds. End quote.

And Allah knows best.