Not so sure about that.
In Clinton v. City of New York [dis-allowing line item veto], Justice Stevens [writing for the majority] was very speific about the process by which a bill becomes law.
And he stated, very clearly, that the President must sign the bill [as written, with no changes] in order for it to become law.
Yes. And he did. With an autopen.
I doubt the President’s use of technology to sign bills while out-of-pocket renders the signature ineffective.
SnakeDoc