The meaning of assent to laws is straightforward: it is the formal approval an authorized official gives to a bill passed by a legislature, and that approval is what turns the bill into enforceable law. In the American system, assent almost always takes the form of a signature by the President or a governor, though the Constitution also allows a bill to become law without one.
Where the Phrase Comes From
“Assent to laws” is language inherited from British constitutional practice. Royal assent is the monarch’s agreement to make a bill passed by Parliament into an Act of Parliament. The Crown technically still holds the right to refuse, but the last time a British monarch actually withheld royal assent was in 1708.1UK Parliament. Royal Assent For three centuries it has been a formality in Britain. In the American colonies it was not.
The Declaration of Independence opens its list of grievances against King George III with exactly this issue: “He has refused his Assent to Laws, the most wholesome and necessary for the public good.”2U.S. National Park Service. The Declaration of Independence: What Were They Thinking? Colonial legislatures would pass laws to address local problems, and the Crown would simply refuse to approve them. That experience shaped how the founders wrote assent into the new Constitution.
What Assent Means Under the U.S. Constitution
Article I, Section 7 replaces royal discretion with a written process. Every bill that passes both the House and the Senate must be presented to the President before it can become law.3Congress.gov. U.S. Constitution Article I Section 7 If the President approves, the signature is the assent, and the bill becomes law.
A signature is the most common form of assent but not the only one. If the President takes no action for ten days (Sundays excluded) while Congress remains in session, the bill becomes law automatically, exactly as if it had been signed.3Congress.gov. U.S. Constitution Article I Section 7 The provision prevents a president from quietly shelving legislation through inaction.
The exception is the pocket veto. If those same ten days expire while Congress has adjourned, the bill dies. Because Congress is not in session to receive the bill back, the President can effectively kill it by doing nothing, and Congress cannot override that outcome because there is no returned bill to vote on.4Congress.gov. Regular Vetoes and Pocket Vetoes: In Brief
Refusing Assent: The Veto
The President can also actively refuse assent by vetoing a bill. This requires returning the bill to the chamber where it originated along with a written explanation of the objections. A veto is not necessarily the last word. Congress can override it if two-thirds of both the House and the Senate vote to pass the bill again, and when an override succeeds, the bill becomes law without presidential assent.3Congress.gov. U.S. Constitution Article I Section 7 The two-thirds threshold is deliberately high, meant to make the veto a real check on Congress without giving the President an absolute one.
No Partial Assent at the Federal Level
A recurring question is whether the President can approve part of a bill and reject the rest. Congress tried to create that power in 1996 with the Line Item Veto Act, which would have let the President cancel individual spending provisions within a larger bill. The Supreme Court struck it down two years later in Clinton v. City of New York.
The Court’s reasoning was direct. The Constitution requires a bill to pass both chambers and be presented to the President as a single package. There is no constitutional authority for the President to amend, repeal, or cancel portions of a statute after signing it. Selective voiding would produce a different law from what Congress actually passed, and the Constitution does not permit that.5Legal Information Institute. Clinton v. City of New York, 524 U.S. 417 (1998) Changing that would take a constitutional amendment, not ordinary legislation. Federal assent is all-or-nothing.
Assent at the State Level
Every state constitution gives the governor a role analogous to the President’s. Bills passed by the state legislature must be presented to the governor, who can sign them, veto them, or in most states let them become law without a signature after a set number of days. Override thresholds vary. Some states require two-thirds, others three-fifths, and a handful allow a simple majority.
The largest structural difference is the line-item veto. Many governors can strike individual spending items from appropriations bills without rejecting the entire measure, a form of selective assent that the Supreme Court has ruled unconstitutional at the federal level. This is why state budget fights often look nothing like federal ones: the governor can pick apart specific provisions rather than accepting or rejecting the whole package.
When an Assented Law Takes Effect
Assent and effective date are not the same thing. By default, a federal law takes effect at the moment of enactment, meaning the point the President signs it, the point a veto override succeeds, or the point the ten-day window expires with Congress in session.6Congress.gov. Understanding Federal Legislation: A Section-by-Section Guide Congress frequently writes a specific effective date into the bill itself, pushing implementation weeks or months out to give agencies and the public time to prepare.
State laws work similarly. Most states set a standard default effective date, often tied to the start of the fiscal year or a fixed calendar date like January 1 or July 1. Legislatures can override the default with an emergency or urgency clause that makes the law effective immediately upon the governor’s signature. These clauses typically require a supermajority and a written justification tied to public safety or welfare.
What an Assented Law Cannot Reach Backward to Do
Assent applies a law from its effective date forward. It does not give the legislature unlimited power to reach into the past. The Constitution’s Ex Post Facto Clause, in Article I, Section 9, bars Congress from passing criminal laws that punish conduct that was legal when it occurred, increase the punishment for past offenses, or change the rules of evidence to make past convictions easier to obtain. No matter how proper the legislative process or how clear the presidential signature, a retroactive criminal law of that kind is unconstitutional on its face.
Civil and tax laws face a looser standard. In United States v. Carlton (1994), the Supreme Court held that retroactive tax legislation is constitutional so long as the retroactive application serves a rational legislative purpose. That is a much easier bar than the criminal one, which is why Congress can pass tax provisions that reach back to the beginning of a calendar year even when signed months later. The line between criminal and civil retroactivity is one of the more counterintuitive parts of constitutional law, and it directly shapes what a newly assented law can actually do.