The latest report may have been the most disturbing -- both for what it said, and what it didn't. The Interior Ministry's human rights ombudsman, Lia Limon, told a packed news conference on February 26 that the Attorney General's Office (PGR) had registered 26,121 people as disappeared during the six-year term of previous President Felipe Calderon.

Of those, Limon said 20,915 had had some type of run-in with the law ("averiguacion previa"). This is the Mexican government's not-so-subtle way of saying that the victims were "guilty of something," and feeds into the public's belief that they must have been disappeared because they were connected to criminal activity.

(That is the same position the Calderon government took, until his team pointed out that he was setting the government up for a series of international civil suits.)

Limon did not give any more information about these disappeared, although parts of these lists seem to have been leaked to the press: first in November to the Washington Post, which broke a story concerning the "over 25,000 people missing," a figure the Post said was from the Attorney General's Office.

Another list of 20,851 went to the Los Angeles Times, which passed it to the non-governmental organization Propuesta Civica. The group published the list in its entirety, after redacting the names of the presumed victims (download the list and Propuesta Civica's excellent analysis of that list here.)

Finally, there is Human Rights Watch, which in a February 20 report said it had obtained two government lists, as well as documenting 249 cases of disappearances itself, some of which were connected to the Mexican Navy, the US government's most important partner in fighting organized crime in that country.

InSight Crime Analysis

For Colombia-watchers, this feels a little like deja vu: embattled government gets large amount of US assistance, and the very military units receiving the aid are then linked to systematic human rights abuses.

In Colombia, one of those units was the Army's 24th Brigade in Putumayo, which, after receiving assistance, gave regular passage and cover to paramilitary groups that were fighting leftist guerrillas, and massacring civilians thought to work with the insurgents. The unit was eventually excluded from receiving aid under the the Leahy Law, a provision that prohibits giving aid to units connected to human rights abuses.

In Mexico, the unit in question is the navy, arguably the most able, and least corrupted, of the Mexican security forces fighting organized crime, and the US government's go-to option. To cite just one example, when the United States got information in late 2009 that Arturo Beltran Leyva, one of Mexico's most feared drug lords, was holed up in a Cuernavaca apartment building, that information went to the Navy, which geared up, organized a raid, and killed Beltran Leyva.

However, in its report, Human Rights Watch said it documented over 20 cases in which the Navy had participated in what it called "enforced disappearances":

The concentration of the cases within a short time period, the similar tactics described by victims' families and other witnesses, corroborated by photographic and video evidence, and the fact that the abductions were spread across three northern states strongly suggests that these were not isolated cases, but rather points to a clear modus operandi by the Navy. Given the number of members of the Navy that allegedly participated in these operations -- at least a dozen official vehicles, according to witness accounts -- and the fact that the Navy acknowledged that it detained several of the victims, it is unlikely that such operations took place without the knowledge of ranking officers.

To be sure, in the northeast, the navy has a reputation for being both brutal and wanton in its treatment of civilians, routinely breaking down doors and using excessive physical force. Even when it does its job, it has a knack for leaving behind a trail of dirt: after killing Beltran Leyva in 2009, for instance, photos emerged showing banknotes spread over the bloodied corpse.

Such disrespect is not easily forgotten. Beltran Leyva's allies, the Zetas, found and killed three members of the family of one navy officer who participated in the raid.

As Human Rights Watch points out, one of the areas hardest hit by disappearances is the northeast. And local organizations say the national numbers barely scratch the surface. The Human Rights Committee of Nuevo Laredo says that in Tamaulipas state alone, where the Zetas and the Gulf Cartel are battling for control, there are over 10,000 disappeared.

The state is also facing down widespread reports of confrontations between security forces and armed groups in which unnamed "aggressors" are killed in "combat" in wildly disproportionate numbers.

The United States now faces a dilemma: apply the Leahy Law and risk cutting off its most important ally (and creating even more sticky relations with the recently elected Enrique Pena Nieto administration); or ignore it and risk causing a furor in the human rights community, which is keeping an ever-closer eye on Mexico.

For its part, the Mexican government seems ready to sweep the "disappearances" under the rug. The government announced it would be working with the Red Cross to clear up the cases. However, in what appears to be a chaos-by-design strategy, it's not clear which government entity is taking the lead on this investigation. What's more, avoiding responsibility is something of a pastime for the country's elites.