THe President can veto a bill before it becomes a law. Once a bill becomes law, the President can not changeit. However, at the risk of being impeached, he can refuse to enforce it, or enforce it selectively, enforcing only the parts he likes, the way that Obama treats the Immigration laws.
the power to impeach
he can sign it and make it a law or he can veto it(reject)
Override a veto
If both houses of congress pass it, it goes to the president. If and when he signs it, it becomes law.
the president sings it.
The president will veto it
If both houses of congress vote by 2/3 to override a presidential veto, it automatically becomes law despite the President's veto.
Here are a few, I am sure there are more. Congress enacts the laws the president has to enforce. This means the president is limited to acts within the scope of power that Congress gives him unless the Constitution gives the president a power that cannot be regulated this way. Congress passes the law that adopts the federal budget. This means that the president can only do as much as the Congress will let him pay for. Congress can impeach a president and then turn him out of office for what the Constitution calls "high crimes and misdemeanors." This ensures that the President follows the laws like everyone else has to. There are many more examples.
10 days
The U.S. Congress passes bills that become Federal Laws when the U.S. President signs them (although there are cases in which Congress can make a bill into a law without the President's approval), and each state Congress passes bills that become state laws when the Governor of the state signs them.
The Supreme Court rules on the constitutionality of laws. However, the president does not make laws. If he does things that are illegal and not in accordance with the law, then Congress can impeach him for misconduct.
The principle of the constitution that states that Congress can impeach a sitting President for unlawful behavior is known as the principle of checks and balances. This principle ensures that no individual, including the President, is above the law and can be held accountable for their actions. Impeachment is a constitutional mechanism that allows Congress to investigate and remove a President from office if they have committed "high crimes and misdemeanors."