Are institutions required to cede review or serve as a Reviewing IRB?

If my institution participates in SMART IRB, is it required to cede review of any or all of its human subjects research? Is my institution required to provide IRB review for other sites?

Unless required by policy or as a condition of participation in a study or research consortium, each Participating Institution elects on a case-by-case basis whether to cede IRB review of or provide IRB review for any research study or studies under the Agreement and whether to participate in any ceded review agreed upon by other Participating Institutions.