In more detail
This amendment to the Amparo Law removed the last paragraph of Article 129 and added a new paragraph to Article 148.
The last paragraph of Article 129 allowed judges to issue stays to prevent the enforcement of actions or laws subject to an Amparo -exceptionally- when they deemed that the public interest would be affected if they deny such measure, rather than if they simply grant it. The deleted paragraph reads:
The Amparo courts may exceptionally grant the stay, even in one of the cases established under this Article, if according to his or her criteria the denial of this suspension may cause a greater impact to the social interests.
On the other hand, the new paragraph added under Article 148 prohibits the issuance of a stay with "general effects" at an Amparo against a law:
In the Amparos regarding the constitutionality of general norms, in no case the stays granted shall have general effects.
Potential consequences:
By eliminating the last paragraph of Article 129 of the Amparo Law, the legislator eliminated the possibility of allowing Amparo judges to grant a stay at an Amparo when they believe that denying such measure would be worse for the public order and social interest, than to grant it. This belittles the legal significance of the weighing that Amparo courts should conduct between the rights of the plaintiff (analyzed prima facie) and the potential adverse effects to the public order, and may result in decisions based more in procedural issues, rather than merits.
On the other hand, the express prohibition to grant a stay with general effects in an Amparo against a law may give room for interpretations and, therefore, injustices, as Amparo judges may deny a stay if they believe that its nature may be of general nature (as opposed to solely protect the legal sphere of the plaintiff). Thus, it could be the case that the Amparo judges may cease to provide a provisional remedy to protect the individuals filing for the Amparo under the excuse that, due to the general nature of the law subject to the Amparo, the effects of the stay may also be general. At the same time, this new paragraph leaves the Amparo against a law with no mechanism to provisionally protect the plaintiff when such plaintiff filed the Amparo defending collective rights.