The federal criminal laws outlaw the numerous ways Americans have of killing and injuring each other, along with the even more numerous ways they have of cheating, deceiving and defrauding each other and their government. It is illegal to repair or recondition gambling devices in the District of Columbia, perhaps because Congress doesn't want amateurs detracting from its own crap shoot. Some of the offenses make you wonder what provoked the law. Americans who are not entitled to cannot go around in the military uniforms of friendly nations, although it is presumably legal to go around dressed like a colonel in Iraq's Republican Guard. It is illegal to impersonate a diplomat, ours or theirs.
Genocide is illegal.
So are assaults with knives, although there is a special penalty if the knife was a switchblade. Some statutes outlaw crimes you might never have thought of, but you're still glad they're on the books. It is illegal to interfere with a lighthouse keeper. Americans are also barred from working aboard slave ships. It is illegal to import honeybee semen.