Ten seconds of Googling:
Rules & Regulations on bringing firearms and guns to Mexico - MEXonline.com
If you take weapons across the border....
You will become on of the dozens of U.S./Foreign citizens arrested each month for violating Mexico's strict firearm and ammunition laws, whether you knew about the law or not;
You will go to jail and your vehicle will be seized;
You will be separated from family, friends and your job, and likely suffer substantial financial hardship;
You will pay court costs and other fees ranging into the tens of thousands of dollars defending yourself;
And worst of all, you may get up to a 30-year sentence in a Mexican prison if found guilty.
Remember, once you cross the border with a firearm or ammunition it is too late! Ignorance of this law will not get you leniency from the police. You will be arrested and sent to jail. Also, the Mexican judicial system is governed by Napoleonic Law which states that you are presumed guilty and must prove your innocence, the opposite of the U.S. laws.
Guns are Illegal in Mexico | U.S. Consulate General Tijuana, Mexico
Don’t bring firearms or ammunition across the border into Mexico.
Don’t carry a knife, even a small pocketknife, on your person in Mexico.
You may become one of dozens of U.S. Citizens who are arrested each month for unintentionally violating Mexico’s strict weapons laws.
If you are caught with firearms or ammunition in Mexico...
You will go to jail and your vehicle will be seized;
You will be separated from your family, friends, and your job, and likely suffer substantial financial hardship;
You will pay court costs and other fees ranging into the tens of thousands of dollars defending yourself;
You may get up to a 30-year sentence in a Mexican prison if found guilty.
If you carry a knife on your person in Mexico, even a pocketknife . . .
You may be arrested and charged with possession of a deadly weapon;
You may spend weeks in jail waiting for trial, and tens of thousands of dollars in attorney’s fees, court costs, and fines;
If convicted, you may be sentenced to up to five years in a Mexican prison.
Claiming not to know about the law will not get you leniency from a police officer or the judicial system. Leave your firearms, ammunition, and knives at home. Don’t bring them into Mexico.
Mexico Guns and firearms
Firearms and Knives
Mexico has some of the strictest gun laws in the world. It is in many ways similar to the United Kingdom, except with much more severe prison terms for even the smallest gun law violations. On the other hand, possession of non-military-caliber small arms by citizens is largely a non-issue. Gun politics are thus not the major issue in Mexico that they are in the neighboring United States, since few Mexican citizens have any gun law difficulties.It is best not to carry even a pocketknife into Mexico as this can result in a weapons charge if a knife is found on a traveler who is arrested for separate offense. Visitors driving across the border should ensure that their vehicles contain no firearms. Mexico imposes harsh penalties for bringing as much as one bullet across its borders.
The US Department of State warns US citizens against taking any firearm or ammunition into Mexico without prior written authorization from the Mexican authorities. Entering Mexico with a firearm, or even a single round of ammunition stuck between the seat cushions of a pickup truck carries a penalty of up to five years in prison, even if the firearm or ammunition is taken into the country unintentionally. Furthermore even a single round of 9 mm ammunition, being a military caliber cartridge, carries even heavier jail-time penalties. The only way legally to import firearms and/or ammunition into Mexico is to secure a permit in advance from the Mexican Embassy in Washington, D.C. or from a Mexican consulate.
Guns are Illegal in Mexico
Be aware if you take weapons across the border
• You will become one of the dozens of U.S. citizens arrested each month for violating Mexico's strict firearm and ammunition law, whether you knew about the law or not.
• You will go to jail and your vehicle will be seized;
• You will be separated from your family, friends and your job, and likely suffer substantial financial hardship;
• Your will pay court costs and other fees ranging into the tens of thousands of dollars defending yourself;
• You may get up to a 30-year sentence in a Mexican prison if found guilty.
REMEMBER, once you cross the border with a firearm or ammunition it is too late.
Ignorance of this law will not get you leniency from the police officer. You will be arrested and sent to jail