In a January ruling, the 9th Circuit Court of Appeals held — in light of the Supreme Court’s ruling striking down part of the Defense of Marriage Act last year — that “classifications based on sexual orientation … are subject to heightened scrutiny.”

While most laws that create groups or classifications must merely show there is a rational basis, or a legitimate reason, for the law, laws subjected to heightened scrutiny — under the Equal Protection Clause of the 14th Amendment to the U.S. Constitution (and applied to the federal government through the 5th Amendment) — must show more. Some, like those that classify based on race, must show a compelling state interest for classifying people, while others, like those based on sex, must show an important state interest in doing so.

Since February 2011, the Obama administration has joined with LGBT advocates in arguing that such heightened scrutiny should be placed on laws that classify based on sexual orientation — and, per other documents since then, gender identity.

The Supreme Court has avoided resolving the question, with opinions by Justice Anthony Kennedy over the past 18 years striking down laws that classify based on sexual orientation on the grounds that they don’t even pass that lowest level of “rational basis” review.