multilevel security

Hi,

I have a question about non-interference rules for MLS. If I have a
subset T1 in T that can send messages to users in a lower clearance
using command Z and they have no other effect on lower level users.
What would the new non-interference rule be? I'm not sure what it might
be since now you have these special subset.

I have so far:

T' = T - T1
C' = C - Z

Thank you.