You will learn in Law School that you can simply check any minority status you want (I would recommend against Native American, as that is easily identifiable - i.e - Tribal status). Check that you are black, Hawaiian (Pacific Islander/Polynesia), Hispanic. there will be no way for the school to "disprove" your heritage.
Unless the schools admissions packet specifically asks for it, or alludes to proof, you are under no affirmative duty to prove your heritage purely for admissions (you may have to prove your ethnicity to claim any other "rights" such as in-state tuition program (certain out-of-state ethnicities may qualify for in-state tuition - i.e. - Out of State Native Hawaiians at the University of Hawaii and other schools) or tuition waivers/grants/scholarships).
You have greater protection against having to prove your ethnicity at a state college, rather than a private college (ie - don't claim you're Native American (Tribally affiliated) if you're not, and use that to get in to, say, BYU...they will toss you for such a indiscretion...but, if you claimed you were Hawaiian, and then didn't seek any sort of minority benefit once in college (scholarship, tuition waiver, book money) you will not be asked to provide proof of heritage/ethnicity.