How to tell when a law is specifically a religious favoring law is very simple. Ask how religion had an effect on the situation before a law was proposed.
Lets take a law for the sake of religious freedom allows religious adoption organiztions not to allow gays to adopt children for religious reasons. Now the religious can be bigoted by law.
In fact it literally allows the law to be broken now sex race sexual preference and religion can be discrimated against BECAUSE of religion.
Was the effect of religion before the law passed? Nothing, religon had no affect on the subject.