On April 21, Mexican newspaper La Jornada  [es] broke the news about an opaque negotiation in the Mexican Congress that purported to pass a reform of the National Security law [Full Text in Spanish].  According to human right groups, political analysts, lawyers and even some politicians, it would legalize the abuses of the army against civilians in the name of national security.
The original project is now on hold. America’s Program reported:
Mexico’s House of Deputies has brought the country to the cusp of a police state. The reform to the National Security Law now before the lower house would grant sweeping military powers to the executive and limit congressional oversight of domestic military activity. It would grant President Felipe Calderón the ability to effectively declare states of exception without congressional approval and unilaterally use the military against any group he deems to be a “threat to internal security.”
Twitter users rapidly started a mobilization against the bill, distributing information about the details of the initiative to alert as many people as possible. @diegoegh quickly put a list with all the links  [es] regarding the coverage of the #LSN  (Ley de Seguridad Nacional; National Security Law) and @asesorpolitico published a Storify  [es] post with relevant press and expert opinions about the #LSN.
A petition to the Congress [es] rejecting the reform quickly started circulating online for signatures.
Red Nacional de Organismos Civiles de Derechos Humanos [es] published an open letter [PDF in Spanish]  to the congressmen asking for a public discussion of the text, recalling the cost of the War on Drugs for Mexico:
Las quejas presentadas ante la Comisión Nacional de Derechos Humanos (CNDH) por violaciones de derechos humanos por parte de militares se han incrementado en un 1,000% entre 2006 y 2009 […] De diciembre de 2006 a finales de 2010, el propio Gobierno Federal contabilizó un número de 34 mil 612 ejecuciones en el contexto de la llamada “guerra contra la delincuencia organizada”.
Human Rights activist Jesús Robles Maloof  [es] blogging at Nexos posted “Who are the obstacles in this country?”  [es], where he explains how the proposed bill could consider peaceful protests and social movements an “obstacle” for national security and this will lead to criminalizing freedom of association, privacy rights and freedom of expression.
Red por la Paz y la Justicia [es] blogs:
No a la reforma de esta ley que legaliza la violación sistemática a nuestras libertades y garantías fundamentales.
Manuel García Estrada published  [es] a letter which he sent to the Congress together with 500 email accounts of congressmen, asking people to demand that the government stop the #LSN.
Javier Briseño writes at Blog On the Go: 
It's a law questioned by many because anything made on the rush will always be a bad idea, in this case, to try to turn our Army to function like cops it's plainly absurd just because there are some obstacles for the Army.
Javier Sicilia, a poet who leads a peaceful movement that demands the end of war and violence in Mexico  named @estamoshastalamadre  (we are fed up), showed up on Wednesday April 27th in Congress  [es] with other prominent activists to demand that the congressmen modify the reform.
Lawyer Rafael Robles Scott blogs at Guru Político  [es]:
Queda abierta la posibilidad de la creación de sistemas de informantes dentro de las mismas estructuras del crimen organizado, la de las negociaciones de sentencias o beneficios para delincuentes a cambio de información para el gobierno, lo que estás comprobado es una forma de corroer las estructuras democráticas de los sistemas de procuración de Justicia[..]
Amnesty International expressed their disappointment  [es] about the #LSN.
The political party PRI (Institutional Revolutionary Party ) voiced their strong support for the reform  [es] and their main backer Alfonso Navarrete, tried to negotiate the reform before the legislation period ended on April 30. Josefina Vázquez Mota from the presidential party tweeted on Wednesday, April 27: 
Hoy en la Cámara, los @diputadospan seguiremos buscando los consensos necesarios para la aprobación de la Ley de Seguridad Nacional.
News blog Animal Politico  [es] published the names and statements of the different politicians that backed the #LSN.
Thanks to the pressure and massive opposition from Mexican society to #LSN, the law was “frozen” temporarily.
Revista Emet [es] reports that now there is a deadline of 90 days to have a new wording of the #LSN to be discussed with experts, civil society and organizations.
However, Mexican citizens remain on alert until the reform is discarded.