The Ohr Hachaim in Parshas Chukas, in which we are given the chok of parah adumah explains why it is referred to as זאת חֻקַּת הַתּוֹרָה, this is the law of the Torah. This is a very inclusive term - wouldn't it be more appropriate to say, this is the law of purifying a person from tumas hameis? He answers that if a person is ready to do the mitzvos with this mindset, because this is what Hashem commanded us to do, then it is as though he was mekayim the whole Torah. Subjugating ourselves and our minds to the will of Hashem serves the entire purpose of the Torah.
This is how we should lead our lives. If we show our willingness to be obedient servants than it is reckoned as though we have already done everything which the Torah has commanded us to do. Perhaps this is the reason why the Torah gave us this mitzvah as a chok. To give us the opportunity to show our allegiance to our Father so that we can follow our Master with complete trust, without seeking to understand or reason.