In a per curiam (by the Court) opinion, they ruled that expenditure limits contravene the First Amendment provision on freedom of speech because a restriction on spending for political communication necessarily reduces the quantity of expression.

Justice Byron White dissented in part and wrote that Congress had legitimately recognized unlimited election spending "as a mortal danger against which effective preventive and curative steps must be taken".

[1] Buckley v. Valeo was extended by the U.S. Supreme Court in further cases, including in the five to four decision of First National Bank of Boston v. Bellotti in 1978[2] and Citizens United v. Federal Election Commission in 2010.

The named defendant in the caption was Francis R. Valeo, the Secretary of the Senate, an ex officio member of the FEC who represented the U.S. federal government.

The major holdings were as follows: The Court's opinion begins by stating certain "General Principles", and then dealing with individual parts of the law in turn.

He said the following:[8] Concededly, neither the limitations on contributions nor those on expenditures directly or indirectly purport to control the content of political speech by candidates or by their supporters or detractors.

Since the contribution and expenditure limitations are neutral as to the content of speech and are not motivated by fear of the consequences of the political speech of particular candidates or of political speech in general, this case depends on whether the nonspeech interests of the Federal Government in regulating the use of money in political campaigns are sufficiently urgent to justify the incidental effects that the limitations visit upon the First Amendment interests of candidates and their supporters.Justice Marshall dissented on the point of limiting personal contributions and expenditures by a candidate to his or her own campaign – he would have upheld that provision, which was stricken by the Court.

But ability to generate contributions may itself depend upon a showing of a financial base for the campaign or some demonstration of preexisting support, which, in turn, is facilitated by expenditures of substantial personal sums.

And even if the advantage can be overcome, the perception that personal wealth wins elections may not only discourage potential candidates without significant personal wealth from entering the political arena, but also undermine public confidence in the integrity of the electoral process.Justice Rehnquist dissented on the application of the public funding provisions to minor parties, believing that it was unconstitutional as applied to them.

Stevens would go on to write the dissent in Citizens United and called for a constitutional amendment to overturn the Court's campaign finance decisions.