Which checks and balances are working in the process of a bill becoming a law?

Congress writes and submits bills to the president for his signature. The president can veto a propose law by submitting within 10 days (not including Sundays) of receiving the bill a written explanation why he does not approve the proposed bill. If he vetoes the bill, congress can override his veto. Both houses of congress must vote by a two-thirds majority to override a presidential veto. If he fails to sign the bill into law and does not provide a written reason within the prescribed ten days, the bill automatically becomes law. The one exception to this is if Congress adjourns before the ten days have lapsed, the bill dies if the president fails to sign it. This procedure is called a pocket veto.