If they are denying the lease due to a criminal history, that is not illegal discrimination. Sellers, landlords, HOAs, etc. may refuse to rent or sell for many reasons--e.g., not liking an applicant's politics. The *only* reasons they can't refuse to sell or rent or those specific reasons made illegal by some law or statute, of which the main reasons are race/color, religion, and disability: there is no discrimination on those bases. However, there is no law prohibiting people from making housing decisions based on a criminal past or criminal history, and, in fact, it is common for rentals, etc. to be denied on this basis. They are allowed to not approve the lease for this reason.