Traditionally, people here just go into the forest and harvest a tree to take home and decorate. Similar to how people might chop down a tree to take home for firewood. We have trillions of trees, so the number used as decorations (or firewood) is relatively small. Some people still do it that way. I don't know what the law would say about that, but if there is a law against it, most likely it is rarely enforced.
Myself, I went to a private tree farm, where these trees were planted (about 10 to 15 years ago) as a crop, for this very purpose. It's basically just a hillside with a creek running through it, and trees of various sizes spaced about 8 feet apart. You can pay someone to chop a tree for you, or you can chop your own. I chopped my own. The cost was 55 Canadian dollars.