My first thought on your question would be, isn't that why the check points weren't put back up because it infringes on a persons ability to travel as per the Mexican constitution(or at least that what I heard)and then we would have to start with the first amendment of the constitution to answer your first question:
Any form of discrimination, based on ethnic or national origin, gender, age, disabilities, social status, medical conditions, religion, opinions, sexual orientation, marital status, or any other form, which violates the human dignity or seeks to annul or diminish the rights and freedoms of the people, is prohibited.
And the next is amendment 11:
Every person has the right to enter and leave the country, to travel through its territory and to move house without the necessity of a letter of safe passage, passport, safe-conduct or any other similar requirement. In the event of criminal or civil liability, the exercise of this right shall be subject to the judicial authority. Relating to limitations imposed by the laws on immigration and public health, or in respect to undesirable aliens residing in the country, the exercise of this right shall be subject to the administrative authority.
And like its already been stated, the Chapala municipality is denying 'senior' discounts on your predial to expats so it all sounds like a "do as I say not as I do" the rules will be made up and changed to suit our needs. YMMV