2010 ADA Standards for Accessible Design Pocket Guide
202.3.1 Prohibited Reduction in Access.
An alteration that decreases or has the effect of decreasing the accessibility of a building or facility below the requirements for new construction at the time of the alteration is prohibited.
35.133 Maintenance of accessible features.
36.211 Maintenance of accessible features.
(c) If the 2010 Standards reduce the technical requirements or the number of required accessible elements below the number required by the 1991 Standards, the technical requirements or the number of accessible elements in a facility subject to this part may be reduced in accordance with the requirements of the 2010 Standards.