When I first started collecting coins as a kid I must admit I pressed coins with a complete ignorance of whether what I was doing was legal or not.  Especially since I was from Canada and have no doubt that some of the very first coins I pressed were probably Canadian currency (Oops!)

But as I got older and got into the hobby a little more seriously I wanted to make sure I wasn’t breaking any laws.  Luckily I started seeing penny machines on my travels that would occasionally have a sign or sticker stating the US codes and that it was infact okay to press coins in these machines.  However each country is different so be sure if you are traveling to a country not listed below that you look into this before the Federales catch up with you.

YES
United States: The United States Codes under Title 18, Chapter 17, and Section 331, “prohibits the mutilation, diminution and falsification of United States coinage.” However, it has been the opinion of some individual officers at the Treasury Department, though without any indication of approval, the foregoing statute does not prohibit the mutilation of coins if done without fraudulent intent or if the mutilated coins are not used fraudulently.

NO
Canada: Section 11(1) of the Currency Act states that “no person shall, except in accordance with a license granted by the Minister of Finance, melt down, break up or use otherwise than as currency any coin that is current and legal tender in Canada.” Furthermore, Section 456 of the Criminal Code of Canada makes it a criminal offence to deface circulation coins: “Every one who: (a)defaces a current coin, or (b)utters a current coin that has been defaced, is guilty of an offence punishable on summary conviction.” The offence is not dependent on fraudulent intent.

Maybe
United Kingdom:  Unfortunately I was unable to find any specific code that stated it was okay to press coins in the UK so I don’t want to say for sure this is acceptable.  However I have found on a few websites that reference the regulation as being the same in the United States.  There are also numerous UK collectors online that state it is okay to press coins as long as they are only pennies and no other denomination.  Again I cannot confirm this for sure and will for now just list this as Maybe.  If I find more concrete evidence I will update this entry.