CAN you grow it? Maybe. . .depends where you live.
As mentioned the plant grows as a tall bush (ie over ten feet high). Its not frost-resistant, so if you get ice or snow where you live (and that covers most of the USA), then you can't really grow it. If you live in Florida or California, or in a desert area (eg Arizona), you might be able to grow it outdoors.
Above freezing it can take a wide variety of temperatures, but it prefers dry climates. Overwater it, and it will die.
You can grow it indoors, or in a greenhouse, but then the plants won't be that big, with correspondingly low yield.
In the USA seeds are legal (since they contain no active ingredient), but growing the plant is not.
That said, bluntly, I doubt most law enforcement would even recognize a
Catha edulis plant if one fell on their head.
Here is a good summary article on growing it:
http://www.plot55.com/growing/c.edulis.html