So, I'm creating an international app; all my team is from Mexico (including me, of course). Which country's law will be applied to it?
The app is physically hosted in the United States, but our "main market" will be of course Mexico.
I'm not a US resident and have no economic activity inside the US; in fact, I don't even have economic activity in Mexico since I'm 14 years old.
The law of each country where you offer the app for download applies, and you have to consider:
Privacy Policy (GDPR in EU, CCPA in California, APPI in Japan, LGPD in Brasil, and more - check each country to be on the safe side)
Disclaimer versus AGB/Terms and Conditions (e.g. Germany), not required but recommended
Impressum (Germany, Switzerland, Austria)
Value Added Tax (VAT) which is taken care of e.g. by Google Play for most countries but not all (e.g. not for Japan) in case the app is not free
Consumer Protection Law - applicable (and different) everywhere
There might be more, but these are the important ones I am aware of.
When publishing an app in a store, such as Apple's App Store, you choose in which countries the app is available. See the instructions on how to do that for the Google Play store, for example.
Smartphone users have to set their base/home country in their smartphones during initial setup (they are able to change it later). They can only download apps that are available for their configured country.
That said, if there is ever a dispute, it will usually be settled according to the laws of the user's country of residence (which may be different from the country configured in their smartphone, but that's another issue).
If you do not make your app available outside Mexico, you should care mostly about Mexico's laws.
Do notice though, though, that laws from the country where you are hosting or processing data will also apply. For example, if you would host in Europe, due to the General Data Protection Regulation (GDPR), you should have to allow users to remove their data from your system if they so wish, even if they are not physically located within EU borders.
It might be worth the time to consult a lawyer to check a few more things. For example, if your app is going to have users that move between Mexico and the US frequently, then you might consider the Children's Online Privacy Protection Act and in the very least not allow people under 13 to have accounts in your system.
To really simplify things, you could find a company that would host your app in Mexico. That would make your life easier regarding international laws.
I am not a lawyer, so as always, talking to an actual lawyer might give you more clarity on these things. In the very least you will be more confident about what you can and cannot do.
The law that applies is the law with the most significant relationship to the dispute in question. This could be, and realistically, usually would be, different for different issues. There could be dozens of different national laws that apply to different issues that could come up.
The laws of every country who says their laws apply apply. If you don't visit those countries and don't have financial interactions with them, then they will find it difficult to enforce their laws. Iran declared a death sentence against Salman Rushdie despite there being no basis for jurisdiction, but they weren't every able to enforce it.
