We all know that the Torah forbids lighting a fire on Shabbat ("And you shall kindle no flame in all your habitations on Shabbat"). And yet, the Kohen Gadol lit the Ner Tamid (i.e. the Menora) in the Mishkan and Bet HaMikdash EVERY day of the week - including Shabbat. And this was not the only exception to Jewish law; the Kohen also wore clothes that mixed wool and linen ("sha'atnez"). Additionally, the cover of the Aron (which contained the 10 Commandments that forbid graven images) had a graven image, the Keruvim, upon it! The rabbis struggle to understand how these exceptions to Torah law could be allowed, particularly in the holiest of all places on Earth. One answer is simply that the very existence of these exceptions was in itself a Chok, a law that defies understanding. But we can also say that an important principle is being illustrated here: Hashem is indicating to us that just as He has the power to create Torah law, so He also has power to suspend, or make exceptions to it, when He sees fit. But also remember that exceptions to the rule are just that: rare instances when the general rule - that G-d must also observe His own commandments - is waived.