http://www.nationalletter.org/aboutTheNli/index.html

NLIs are required to be accompanied by an financial aid agreement, but a financial aid agreement doesn't require an NLI. An aid agreement is just confirming that if the athlete attends that school, the school is committed to giving them then scholarship and if the athlete does begin attendance, they must commit to the conditions to receive the scholarship money. But the agreement does not bind them to the school, only the NLI does. The athlete could sign an aid agreement at 5 schools prior to enrollment. The NLI is the one that has the teeth. However, an NLI can only be signed during the appropriate national signing periods for qualifying athletes. Kingsley cannot sign an NLI because he currently does not meet the conditions or fall within the signing period. An financial aid agreement is all he can sign. Therefore, he could still back out of BYU.