Article I, Section 7, Paragraph 2

Signing statement is president's first since 2006
Boston Globe
By Charlie Savage
Globe Staff / December 1, 2007
WASHINGTON - President Bush this month issued his first signing statement since the Democratic takeover of Congress, reserving the right to bypass 11 provisions in a military appropriations bill under his executive powers.

... "The Act contains certain provisions identical to those found in prior bills passed by the Congress that might be construed to be inconsistent with my Constitutional responsibilities," Bush's statement says.

"To avoid such potential infirmities, I will interpret and construe such provisions in the same manner as I have previously stated in regard to those provisions."

U.S. Constitution
Article I, Section 7, Paragraph 2
"Every bill which shall have passed the House of Representatives and the Senate, shall, before it become a law, be presented to the President of the United States; if he approve he shall sign it, but if not he shall return it, with his objections to that House in which it shall have originated..."

Nothing here about "signing statements". Two choices:
1) approve the bill
2) return to the House in which it originated

And a bonus!
U.S. Constitution
Article II, Section 3, paragraph 1
"... he [The President] shall take care that the laws be faithfully executed..."