Can a prison regulation restrict an inmate's right to exercise his religion?

Plaintiff alleges that Muslim inmates were denied religious services for over a year. "Inmates clearly retain protections afforded by the First Amendment... including its directive that no law shall prohibit the free exercise of religion." O'Lone v. Estate of Shabazz, 482 U.S. 342, 348 (1987) (citations omitted). However, "[l]awful incarceration brings about the necessary withdrawal or limitation of many privileges and rights, a retraction justified by the considerations underlying our penal system." Id. (citation and internal quotation marks omitted). A prison regulation may therefore impinge upon an inmate's right to exercise his religion if the regulation is "reasonably related to legitimate penological interests." Shakur v. Schriro, 514 F.3d 878, 884 (9th Cir. 2008) (citations omitted). In contesting the validity of a prison regulation, an inmate must also show that his religious practice is "sincerely held" and "rooted in religious belief. Id. at 884-85.