A lot of the discussion around Robert Mueller’s investigation of Trump and his various co-conspirators is the possibility of presidential pardons undermining the investigation. So far, it hasn’t happened yet—but Trump often hints about it, and many think it’s a not-too-subtle signal to potential witnesses and folks getting squeezed by the special prosecutor: refuse to cooperate, and sooner or later, you’ll be let out of jail free.
One of the defenses against pardons being used to undermine justice, of course, is the possibility of state charges against many of the principals. Much of the alleged activity, particularly when it comes to general organized crime rather than the political intrigue, happened within the State of New York and is subject to its jurisdiction, and New York is reputed to have far nastier facilities for convicts than those operated by the US Bureau of Prisons.
But with the policy of ripping families apart at the border—something that has outraged many of Trump’s supporters on the right, and virtually everyone on the left—opens up a new possibility: the possibility of trial, for various crimes against humanity, of Trump and many others in his administration. Obviously, Cohen won’t be brought up on such a charge, but the POTUS could be, as could secretary of DHS and others involved in implementing the policy.
Remember: The POTUS cannot pardon this; as it is beyond the jurisdiction of the United States. Nor is either color of law or “just following orders” accepted as an excuse here; the whole purpose of this category of offense is to exact justice against government leaders who, while possibly acting under the lawful authority of where they happen to govern (especially if they get to say what “lawful authority” is), do things that violate basic human rights.
(And barring that, there’s always the possibility of trial in Mexico...)
International law is, I’ll admit, a tricky subject and one I’m only vaguely familiar with. Many of the political norms that Trump and his cronies have smashed recently are, as far as the global community is concerned, inside baseball. But the child separation policy seems to have crossed a big bright line, one that past outrages (including the “Muslim ban” and stepped-up deportation of illegal immigrants already inside the US) only approached, and opened the DOTUS up to a new avenue of prosecution, one that he can’t evade by a stroke of his own pen.