42 C.F.R. § 416.25
Basic requirements
Participation as an ASC is limited to facilities that—
(a) Meet the definition in § 416.2; and
(b) Have in effect an agreement obtained in accordance with this subpart.
Participation as an ASC is limited to facilities that—
(a) Meet the definition in § 416.2; and
(b) Have in effect an agreement obtained in accordance with this subpart.