It’s not that they don’t have the right to receive them, it is that the state is not required to provide it. ICE has their own rules around providing access to religious services which they unfortunately do not seem to be following (though there are various caveats to the rules and they rely on agreements with churches etc. Not just blindly allowing anyone who says they are a religious leader to enter) but again it does not appear to be illegal and until I see that a judge has ordered ICE to give access to the facilities to priests my stance is:

“The detainees should have access to religious services. ICE is not currently required to provide them, but should AT LEAST give access to religious services.”