Subject to subsection (b) of this section, the Board may not issue: a Class B license for a restaurant that is within 400 feet of the nearest point of a public school building; or any other license for an establishment that is within 500 feet of the nearest point of a public school building. A decision of the County Board of Education to locate a public school building within 500 feet of the premises of a license holder may not be the basis to revoke or deny the renewal or transfer of the license. For a license issued on or before June 30, 1971, the Board may renew the license or approve the transfer of the license to a new license holder for the same establishment and type of license. The prohibition against issuing a license in subsection (a) of this section does not apply to the issuance of a gift basket permit.