In the National Defense Authorization Act for 2008, Congress prohibited the use of federal funds to “to establish any military installation or base for the purpose of providing for the permanent stationing of United States Armed Forces in Iraq” or “to exercise United States control of the oil resources of Iraq.” it also,

….requires intelligence agencies to turn over “any existing intelligence assessment, report, estimate or legal opinion” requested by the leaders of the House and Senate armed services committees within 45 days. If the president wants to assert executive privilege to deny the request, the law says, White House counsel must do so in writing.

Finally, Bush’s signing statement raised constitutional questions about a section of the bill that established an independent, bipartisan “Commission on Wartime Contracting in Iraq and Afghanistan” to investigate allegations of waste, mismanagement, and excessive force by contractors.

Bush’s response, “Nyah, nyah, nayh, I’m president“, in a signing statement.

A prohibition on spending by the congress is legally binding on a president, even it makes his job “hard work”.

This is why having impeachment on the table is a necessary thing:

NOT ON THE TABLE! NOT ON THE TABLE!