(a) General rule.— Except as provided in subsection (b), a municipality or local authority shall not have the power to mandate that:

1. (1) a seller or an agent of either or both the seller and the buyer make any particular disclosures to the buyer in connection with a residential real estate transfer; or
2. (2) provisions on any particular subject be included in an agreement of transfer.

(b) Exception.— Subsection (a) shall not apply to an ordinance or regulation adopted by a municipality or local authority before the effective date of this section, and such an ordinance or regulation shall continue in full force and effect, except that the municipality or local authority shall not have the power after that date to amend the ordinance or regulation in a manner that:

1. (1) imposes new or expanded disclosure requirements;
2. (2) increases the scope of any provision that must be included in an agreement of transfer; or
3. (3) imposes new requirements on any agent, buyer or seller involved in a residential real estate transfer.