(2) Prohibited Regulation. A Municipality shall not subject the use of land or structures on a Lot for a Protected Use ADU to any of the following:

1. (a) Owner-Occupancy Requirements. A requirement that either the Protected Use ADU or the Principal Dwelling be owner-occupied.

2. (b) Minimum Parking Requirements. A requirement of, as applicable:

   1. 1. More than one additional on-street or off-street parking space for a Protected Use ADU if all portions of its Lot are located outside a 0.5 mile radius of a Transit Station; or
   2. 2. Any additional on-street or off-street parking space for a Protected Use ADU if any portion of its Lot is located within a 0.5 mile radius of a Transit Station.
3. (c) Use and Occupancy Restrictions. A requirement that a Protected Use ADU be subject to a Use and Occupancy Restriction.
4. (d) Unit Caps & Density. Any limit, quota or other restriction on the number of Protected Use ADUs that may be permitted, constructed, or leased within a Municipality or Zoning District. Protected Use ADUs shall not be counted in any density calculations.
5. (e) Relationship to Principal Dwelling. A requirement that a Protected Use ADU be attached to or detached from the Principal Dwelling.

(3) Unreasonable Regulation.

1. (a) A Municipality may reasonably regulate and restrict Protected Use ADUs provided that any restriction or regulation imposed by a Municipality shall be unreasonable if the regulation or restriction, when applicable to a Protected Use ADU:

   1. 1. Does not serve a legitimate Municipal interest sought to be achieved by local Zoning;
   2. 2. Serves a legitimate Municipal interest sought to be achieved by local Zoning but its application to a Protected Use ADU does not rationally relate to the legitimate Municipal interest; or

   3. 3. Serves a legitimate Municipal interest sought to be achieved by local Zoning and its application to a Protected Use ADU rationally relates to the interest, but compliance with the regulation or restriction will:

      1. a. Result in complete nullification of the use or development of a Protected Use ADU;
      2. b. Impose excessive costs on the use or development of a Protected Use ADU without significantly advancing the Municipality’s legitimate interest; or
      3. c. Substantially diminish or interfere with the use or development of a Protected Use ADU without appreciably advancing the Municipality's legitimate interest.

2. (b) Municipalities shall apply the analysis articulated in 760 CMR 71.03(3)(a) to establish and apply reasonable Zoning or general ordinances or by-laws, or Municipal regulations for Protected Use ADUs, but in no case shall a restriction or regulation be found reasonable where it exceeds the limitations, or is inconsistent with provisions, described below, as applicable:

   1. 1. Design Standards. Any Design Standard that:

      1. a. Would not be applied to a Single-family Residential Dwelling in the Single- family Residential Zoning District in which the Protected Use ADU is located or
      2. b. Is so restrictive, excessive, burdensome, or arbitrary that it prohibits, renders infeasible, or unreasonably increases the costs of the use or construction of a Protected Use ADU.
   2. 2. Dimensional Standards. Any requirement concerning dimensional standards, such as dimensional setbacks, lot coverage, open space, bulk and height, and number of stories, that are more restrictive than is required for the Principal Dwelling, or a Single- family Residential Dwelling or accessory structure in the Zoning District in which the Protected Use ADU is located, whichever results in more permissive regulation, provided that a Municipality may not require a minimum Lot size for a Protected Use ADU.
   3. 3. Utilities, Safety, and Emergency Access. Any requirement concerning utilities, safety and emergency access that is more restrictive than is permitted by state requirements, including under the Fire Code. A Municipality may not require a separate utility connection, such as water, sewer, electric, provided that a separate connection may be required by a Municipal or regional utility, investor-owned utility; by state law; by a local, regional, or state board or commission; or by court order.
   4. 4. Environmental Regulation. Any regulation for the protection of public health, safety, welfare and the environment pursuant to 310 CMR 15.000: The State Environmental Code, Title 5: Standard Requirements for the Siting, Construction, Inspection, Upgrade and Expansion of On site Sewage Treatment and Disposal Systems and for the Transport and Disposal of Septage, that is more restrictive than is required for a Single-family Residential Dwelling in the Zoning District in which the Protected Use ADU is located.
   5. 5. Site Plan Review. Site Plan Review concerning the Protected Use ADU that is not clear and objective or imposes terms and conditions that are unreasonable or inconsistent with an as-of-right process as defined in M.G.L. c. 40A, § 1A.
   6. 6. Impact Analysis, Studies, and Fees. Any requirement for any impact analysis, study, report, or impact fee that is not required for the development of a Single-family Residential Dwelling in the Single-family Residential Zoning District in which the Protected Use ADU is located.
   7. 7. Modular Dwelling Units. Any requirement that prohibits, regulates or restricts a Modular Dwelling Unit from being used as a Protected Use ADU that is more restrictive than the Building Code.
   8. 8. Historic Districts. Municipalities may establish Design Standards and Dimensional Standards for Protected Use ADUs located in an Historic District that are more restrictive or different from what is required for a Single-family Residential Dwelling, or Principal Dwelling, in the Single-family Residential Zoning District; provided, however, that such standards are not unreasonable pursuant to 760 CMR 71.03(3)(a).
   9. 9. Pre-existing Nonconforming Structures. A Municipality may not prohibit the development of a Protected Use ADU in an existing structure or Principal Dwelling, or Lot due to nonconformance, that could be used for, or converted into, a Protected Use ADU in conformance with the Building Code, 760 CMR 71.00, and state law.
3. (c) Short-term Rentals. Municipalities may establish restrictions and prohibitions on the Short-term Rental of Protected Use ADUs pursuant to M.G.L. c. 64G.