President Barack Obama used his veto authority only four times during his tenure in the White House, the fewest of any president who completed at least one term since Millar Fillmore in the mid-1800s, according to data kept by the U.S. Senate.

Obama used his veto power even more scarcely than did his predecessor, President George W. Bush, who vetoed a total of 12 bills during his two terms in the White House.

When both chambers of Congress – the House of Representative and the Senate – pass a bill, the legislation goes to the presidents desk for signature into law. If the president favors the law, hell sign in. If the bill is important enough, the president often uses numerous pens while writing his signature. 

Once the bill arrives on the presidents desk, he has 10 days to either sign it or reject it. If the president does nothing the bill becomes law in most cases. If the president vetoes the bill, he often returns it to Congress with an explanation for his opposition.

Heres a list of the bills vetoed by Barack Obama during his two terms in office, an explanation of why he vetoed the bills and what the bills would have done if signed into law.

Obama vetoed the Keystone XL Pipeline Approval Act in February of 2015 because it would have circumvented his administrations authority over whether the project to carry oil from Canada to the Gulf of Mexico should be undertaken  The Keystone XL Pipeline would carry oil across 1,179 miles from Hardisty, Alberta, to Steele City, Nebraska. Estimates have placed the cost of building the pipeline at $7.6 billion.

Through this bill, the United States Congress attempts to circumvent longstanding and proven processes for determining whether or not building and operating a cross-border pipeline serves the national interest, Obama wrote in a veto memo to Congress.

The Presidential power to veto legislation is one I take seriously. But I also take seriously my responsibility to the American people. And because this act of Congress conflicts with established executive