In the USA the laws vary in every state.
I can tell you that in Oregon after 2006 you can't get one street legal unless you can get a letter from the manufacture stating that the bike will pass current EPA emission standards and it's a sure bet that you will not get that letter
.
Those that got them street approved before 2006 are in the clear.
I have heard of one exception in that you are allowed to build one custom bike a year.
If this is so, then you better make sure that all the manufactures logos are removed before taking your bike to the DMV for approval.
Also, you will need a steel tank, DOT approved tires, and all the rest of the lights, horn, speedo, odo, ect.
Even then your request may get kicked up to Salem for approval.
Of course the easiest thing to do would be to get a frame and Title of one that has already been done.
There are a few of them out there, but not many.