Does not implementing a setter method in ActionScript 3 make the property unsettable?

Assuming that I define an ActionScript 3 class as follows:

package com.fluther {
public class Fluther {
private var _property:Object;
public function Fluther (property:Object) {
this.property = property;
}
public function get property ():Object {
return _property;
}
}
}

Does the lack of a set method for property make property unsettable except through the constructor? If that is not the case, how should the set method be implemented so as to make property gettable but not settable (by throwing an IllegalStateError?)?

And assuming that I