As you've probably heard, the Quansheng UV-K5 is the hot new HT. And there is a good reason it is so popular. I've been having a lot of fun with mine, and I would highly recommend getting one. 2m FM is fun, and 2m SSB or CW is even funner. And if you choose the same firmware to load as I did (uvk5cec), it will transmit APRS and SSTV.
I made a video going over how mine is setup. Hopefully it helps if you have one. And I'm sure there'll be more videos coming with it in use. The CQ VHF contest is just a week away....
I am licensed to use this equipment in the United States, but nearly all countries have some sort of requirements for licensing the use of radio spectrum.
https://en.m.wikipedia.org/wiki/Amateur_radio
As for enforcement, it depends on what you are doing with it. If you just buy one and start using it, it is possible that you can (accidentally or intentionally) interfere with other people's radio communication. This might mean you cause problems with someone's WiFi, or it might mean you interrupt air traffic communication or police radios.
If you use it a lot, and interfere with important traffic, then someone can use radio receiving equipment to triangulate your position (it's not super easy, but it's not too difficult to do with the right equipment)
Some radio operators do this for sport, but the FCC can and will track down major offenders.
https://en.m.wikipedia.org/wiki/Amateur_radio_direction_finding
Depending on how poorly you operate illegal radios, you can go to jail.