Is this a T?

[Adam]

Originally Posted by blindzebra

The thrower isn't allowed to step onto the court before releasing the throw-in...A1 sets it down and goes inbounds, they can't go back and throw it in, IMO.

This rule applies to spot throwins only.
I don't have my rule book, but I'm pretty sure there's no rule that prevents the following scenario:

1. A1 grabs ball for an endline throwin.
2. A2 steps out of bounds and takes the ball from A1.
3. A1 runs in bounds and around some defenders, then back out of bounds on the other side of the lane from A2.
4. A2 throws a pass to A1, now standing OOB.
5. A2 passes inbounds to A3.

Likewise, nothing in the rules prevents a would-be thrower from going inbounds and then back out of bounds to get the ball during the endline throwin.