how to limit access to common objects shared among multiple threads

Lets say I have two threads which "communicate" via a shared object (passed to them as a reference when they are created). The shared object is primarily composed of getters and setters. In quite a few instances the two threads need access to both types of methods. However, in some only one of the threads
should access the setter method. Eg, the control thread should be the only one able to call the method set_LimitSwitchStautus(true); it makes no sense (nor would it be desirable) for the GUI thread to do so. The basic structure of the program is something like:

class Limits {
bool fLimit;
bool get_Limit() const;
void set_Limit(bool);
}

class Common {
Limits Limit;
plus a whole bunch more such contained objects
}

main {
Common blotz;
CntrlThread tCntrl(blotz);
GuiThread tGui(blotz);

tCntrl.start(); << I am using ZThreads
tGui.start();
}

where I'd like code to fail to compile (or at least do nothing) if the
GUI thread were to call set_Limit.