Subject to

“Subject to” is one of those bits of technical language that can easily cause misunderstandings for the unwary. It comes up frequently in legislation and often leads to mistakes.

A rule that is described as subject to something else, is subordinate to that thing. So, if Rule A is subject to Rule B, Rule A is subordinate to Rule B.

In other words, it will take effect, only so far as Rule B does not apply.

This is much easier to see in practice.