Is it permissible for us to trade in a public place that was usurped, having been owned by another person for a year before it was left to us, knowing that the place is state property and we do not know its original owner?

If trading in a public place does not harm Muslims, then it is permissible to trade there until the original person who was trading there first requests it, because he has more right to it than others. Usurping this place from him does not invalidate his right, based on the Prophet’s (peace be upon him) saying: "None of you should make his brother stand up from his seat to sit in it," and his saying: "If one of you stands up from his seat and then returns to it, he has more right to it." Scholars have used these hadiths to deduce that a vendor's spot in a public place, which he has customarily occupied, gives him more right to it until he achieves his purpose.

However, if trading in this place harms Muslims, then it is not permissible for anyone to trade there.