WASHINGTON — The Supreme Court on Tuesday agreed to hear a challenge to federal campaign contribution limits, setting the stage for what may turn out to be the most important federal campaign finance case since the court’s 2010 decision in Citizens United, which struck down limits on independent campaign spending by corporations and unions.
The latest case is an attack on the other main pillar of federal campaign finance regulation: limits on contributions made directly to political candidates and some political committees.
“In Citizens United, the court resisted tinkering with the rules for contribution limits,” said Richard L. Hasen, an expert on election law at the University of California, Irvine. “This could be the start of chipping away at contribution limits.”
The central question is in one way modest and in another ambitious. It challenges only aggregate limits — overall caps on contributions to several candidates or committees — and does not directly attack the more familiar basic limits on contributions to individual candidates or committees. Should the court agree that those overall limits are unconstitutional, however, its decision could represent a fundamental reassessment of a basic distinction established in Buckley v. Valeo in 1976, which said contributions may be regulated more strictly than expenditures because of their potential for corruption.
The case was brought by Shaun McCutcheon, an Alabama man, and the Republican National Committee. Mr. McCutcheon said he was prepared to abide by contribution limits to individual candidates and groups, which are currently $2,500 per election to federal candidates, $30,800 per year to national party committees, $10,000 per year to state party committees and $5,000 per year to other political committees. But he said he objected to separate overall two-year limits, currently $46,200 for contributions to candidates and $70,800 for contributions to groups, arguing that they were unjustified and too low.
He said he had made contributions to 16 federal candidates in recent elections and had wanted to give money to 12 more. He said he had also wanted to give $25,000 to each of three political committees established by the Republican Party. Each set of contributions would have put him over the overall limits.
In September, a special three-judge federal court in Washington upheld the overall limits, saying they were justified by the need to prevent the circumvention of the basic limits.
“Although we acknowledge the constitutional line between political speech and political contributions grows increasingly difficult to discern,” Judge Janice Rogers Brown wrote for the court, “we decline plaintiffs’ invitation to anticipate the Supreme Court’s agenda.”
In June, in a brief, unsigned 5-to-4 decision, the Supreme Court affirmed the Citizens United ruling, summarily reversing a decision of the Montana Supreme Court that had upheld a state law limiting independent political spending by corporations.
“The question presented in this case is whether the holding of Citizens United applies to the Montana state law,” the opinion said. “There can be no serious doubt that it does.” Montana’s arguments, the opinion continued, “either were already rejected in Citizens United, or fail to meaningfully distinguish that case.”
In 2006, in Randall v. Sorell, the Supreme Court struck down Vermont’s contribution limits, the lowest in the nation, as unconstitutional. Individuals and political parties were not allowed to contribute more than $400 to a candidate for statewide office over a two-year election cycle, including primaries. In a brief concurrence, Justice Samuel A. Alito Jr. said there was no reason to address the continuing validity of Buckley v. Valeo in that case, suggesting that a later case might present the question directly.
The latest case, McCutcheon v. Federal Election Commission, No. 12-536, may be that case.
The court also issued a pair of Fourth Amendment decisions on Tuesday.
In one of them, the court ruled, 6 to 3, that the police may not stop and detain people without probable cause in connection with a search warrant once they had left the premises being searched.
The case, Bailey v. United States, No. 11-770, concerned Chunon Bailey, a New York man who left an apartment in 2005 as it was about to be searched. The police had a warrant to look for a gun, which they ultimately found. They also followed Mr. Bailey’s car for about a mile before stopping, handcuffing and searching him.
Mr. Bailey was later convicted of gun and drug charges. He asked lower courts to suppress evidence from the stop — statements he made and a key linking him to the apartment — but they refused, relying on Michigan v. Summers, a 1981 Supreme Court decision allowing the detention of people in the immediate vicinity of the place to be searched.
Justice Anthony M. Kennedy, writing for the majority, said none of the interests justifying the detention of people at the scene had allowed Mr. Bailey to be detained. People far from the scene cannot endanger officers conducting the search or disrupt it, he said. Nor could the interest in “preventing flight” be stretched, he wrote, to “justify, for instance, detaining a suspect who is 10 miles away, ready to board a plane.”
Justice Kennedy added that a detention in public gave rise to a different sort of indignity than one inside a home.
Chief Justice John G. Roberts Jr. and Justices Antonin Scalia, Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan joined the majority opinion.
In a second, unanimous ruling, the court decided the first of two cases concerning dog sniffs on its docket this term, Florida v. Harris, No. 11-817.
The case concerned a man, Clayton Harris, who was pulled over in 2006 near Bristol, Fla., for driving with an expired license plate. A police dog named Aldo alerted his human partner to contraband in Mr. Harris’s pickup truck.
Based on the alert, the officer searched the truck and found ingredients for making methamphetamine.
The Florida Supreme Court suppressed the evidence, saying that prosecutors had not adequately established the reliability of Aldo’s nose through comprehensive documentation of his performance in earlier searches. Justice Kagan said the dog’s substantial training and certification sufficed.
“A sniff is up to snuff when it meets that test,” she wrote.
The case was argued in October on the same day as Florida v. Jardines, No. 11-564, concerning dog sniffs outside a home, and there was reason to think the two cases would be decided together. But the justices apparently found the question in the second case harder.