Pool is one of the lawful games since it doesn’t involve any Sharia’s violation nor based on betting or speculating; rather, it is based on skill and accuracy. However, if it was meant as a mean for gambling on cash then it is prohibited for this reason, due to the fact that gambling is widely spread within pool halls whereas the loser bears the cost of the table in case of loss and both parties will be involved into prohibited gambling, for Allah, The Exalted said (What means):” O ye who believe! Strong drink and games of chance and idols and divining arrows are only an infamy of Satan’s handiwork. Leave it aside in order that ye may succeed. [5:91]
Satan seeketh only to cast among you enmity and hatred by means of strong drink and games of chance, and to turn you from remembrance of Allah and from (His) worship. Will ye then have done ?. [Al-Maidah/90-91].
Yet, there is no harm in leasing the above hall so long as the latter violation don’t exist in it; especially, that the Questioner will condition that nothing contrary to the ruling of Sharia and civil law will be committed in it.
Finally, if the leasee didn’t abide by the aforementioned condition and used the hall as an umbrella to commit unlawful acts, then the leaser is obliged to annul the leasing contract in order to avoid giving a hand or being a part in committing prohibited acts. And Allah knows best.