Having studied the Constitution and US political process in my past education, I believe that laws are signed into effect by the executive branch or vetoed. The legislative branch may override a veto and effect the law or may allow the veto to stand.

With regard to the Economic Stimulus legislation, I would suggest setting your personal "Wayback Machine" to January 2008 and scan the news of that time, paying particular attention to what the current resident of the White House and Treasury Secretary Paulson were requesting from Congress.