Adultery and discrimination

An interesting argument has been advanced in a U.S. Air Force court-martial. According to this Colorado Springs Gazette article:

Lawyers for a Schriever Air Force Base colonel argued Monday that a half-dozen adultery charges against him should be thrown out because the military's law banning extramarital sex discriminates against heterosexuals. 

Col. Eugene Marcus Caughey is headed for an August court-martial on charges of rape, assault, taking a dirty selfie and the adultery counts. He was in court Monday for a formal reading of the charges and to argue pretrial motions. 

Maj. Keith Meister, one of three attorneys defending Caughey, told Air Force judge Col. Wes Moore that the military's definition of adultery as sex between a man and a woman hasn't keep place with its definition of marriage, which now includes same-sex couples. That's because the military's adultery law requires "sexual intercourse" as an element of guilt, which the Pentagon defines as an act between a man and a woman.

The defense motion mistakenly invokes the equal protection clause of the Fourteenth Amendment:

Caughey's defense team maintains that because gay people get a pass, the charges violate the colonel's rights under the 14th Amendment, which mandates equal protection under law.

The Fourteenth Amendment applies only to the states, and not to the federal government. There is, however, an equal protection component to Fifth Amendment due process. E.g., Bolling v. Sharpe, 347 U.S. 497 (1954).