Mexican law is based on the Roman and Napoleonic codes, presuming an accused person guilty until proven innocent.
A law passed in 2009 determined that possession of small amounts of certain drugs for personal use – including cannabis (5g), cocaine (500mg), heroin (50mg) and methamphetamine (40mg) – would not incur legal proceedings against first-time offenders. But those found in possession of small amounts may still have to appear before a prosecutor to determine whether it is for personal use. The easiest way to avoid any drug-related problems is not to use them. As of June 2017, the medicinal use of marijuana is legal.
It’s against Mexican law to take any firearm or ammunition into the country (even unintentionally).
Police corruption is a big problem in Mexico. If confronted by police soliciting bribes for bogus driving offences, you can either pretend to speak no Spanish, or else hand over photocopies of your legal documents (not the documents themselves), ask for their names and badge numbers and call their bluff by offering to accompany them to the police station.
Useful warnings on Mexican law are found on the website of the US State Department (http://travel.state.gov).
Getting Legal Help
If a foreigner is arrested in Mexico, the Mexican authorities, according to international law, are supposed to promptly contact the person’s consulate or embassy if asked to do so. They may not. If they do, consular officials can tell you your rights, provide lists of lawyers, monitor your case, try to make sure you are treated humanely and notify your relatives or friends – but they can’t get you out of jail. By Mexican law, the longest a person can be detained without a specific accusation after arrest is 48 hours (though official arrest may not take place until after a period of initial questioning).
Tourist offices in Mexico, especially those run by state governments, can often help you with legal problems such as complaints and reporting crimes or lost articles. The national tourism ministry, Sectur, has a toll-free number offering 24-hour telephone advice.
If you are the victim of a crime, your embassy or consulate, or Sectur or state tourist offices, can give advice. In some cases, there may be little to gain by going to the police, unless you need a statement to present to your insurance company. If you go to the police, take your passport and tourist permit, if you still have them. If you just want to report a theft for insurance purposes, say you want to ‘poner una acta de un robo’ (make a record of a robbery). This should make it clear that you merely want a piece of paper, and you should get it without too much trouble.