oob throw in

[Steve_pa]

On throw in from out of bounds can thrower step on line. Or does he have to step onto the court side of line to be a violation?

[ROMANO]

Yes.
On throw in from out of bounds the thrower can step on the line.

[just another ref]

The line is out of bounds, so standing on the line is the same as standing outside the line. If you think of it, some courts do not even have a line, but instead the entire out-of-bounds area is a different color than the court.