<p>Technically Princeton cannot make their early decisions legally binding; in other words, if you get accepted to another school regular decision and that school allows you to go there (and decides not to honor Princeton's ED contract) then there is unfortunately nothing that Princeton can do.</p>
<p>However, opting out of an early decision contract is bad form and shows a serious lack of integrity and ethics on the part of the applicant. If I was a school I certainly wouldn't let someone attend who had breached an early decision contract, but I am not Harvard...</p>