John McCain is using the Supreme Court's landmark ruling on gun control Thursday as fresh ammunition against Barack Obama, accusing the presumptive Democratic presidential nominee of flip-flopping over his position on the District of Columbia handgun ban.

The 32-year-old ban was invalidated by the court's decision, which found Americans have a constitutional right to keep guns in their homes for self-defense.

But Obama's campaign has offered conflicting messages on the controversial D.C. law.

After his campaign said in a statement to The Chicago Tribune last year that "Obama believes the D.C. handgun law is constitutional," an Obama spokesman told ABC News this week that that statement was an "inartful attempt" to characterize the candidate's position.

Obama said Thursday the Supreme Court basically agreed with him on gun control.

"All I can say (is) it's one in a long ... series in reversals of positions," McCain said Thursday, asked about the discrepancy. "In a few days he has gone from opposing nuclear power, to not being a proponent, to willing to explore.

"I fully anticipate -- whether it be on his pledge on public financing or his position on the Second Amendment or any other issues -- he is changing his positions," he said. "So it's not surprising."

The presumptive GOP nominee has tried to make the flip-flopper tag stick, accusing Obama of reversing course on a prior pledge to take public financing for the general election, and now equivocating on gun rights. Obama has done the same, accusing McCain recently of reversing course to oppose the federal ban on offshore oil drilling.

McCain released a statement applauding the Second Amendment decision Thursday, while Obama released one later saying the Supreme Court decision has "endorsed" his view.

Obama also told FOX Business Network that he has "said consistently that I believe that the Second Amendment is an individual right, and that was the essential decision that the Supreme Court came down on.

"And it also recognized that even though we have an individual right to bear arms, that that right can be limited by sensible, reasonable gun laws," he said.

In public, though, Obama has spoken carefully and broadly about the D.C. handgun ban. Asked about the Supreme Court case Wednesday, Obama said he would not speculate on the coming decision. He said he supports the Second Amendment, but that local governments should have the right to provide "common sense gun laws" to keep firearms out of the wrong hands.

In other instances, Obama refused to articulate a position when asked whether he thought the D.C. ban was constitutional.

Other than a few departures, McCain is largely in line with the National Rifle Association's hardline support for gun rights. He voted against a ban on assault-style weapons and for shielding gun-makers and dealers from civil damage suits. But he broke with the NRA to favor requiring background checks at gun shows and has taken heat for pushing through campaign finance legislation that gun-rights advocates say muzzled their free speech.

Obama has voted to leave gun-makers and dealers open to lawsuits. He also took largely liberal positions on gun laws while in the Illinois legislature, including backing a ban on all forms of semiautomatic weapons and tighter state restrictions generally on firearms.

Though Obama's spokesman said the statement that the D.C. law is constitutional was "inartful," Obama himself did not correct a debate moderator who repeated the position in February.

"You said in Idaho recently, I'm quoting here, 'I have no intention of taking away folks' guns.' But you support the D.C. handgun ban and you've said that it's constitutional," said the moderator, Leon Harris of Washington television station WJLA. Obama nodded as Harris spoke, nodding and saying, "Right, right."

The Obama campaign argued that Obama was simply acknowledging the question by saying "right."

The campaign would not answer directly Thursday when asked whether the candidate agreed with the court that the D.C. ban was unconstitutional, simply pointing back to his statement.

Obama's written statement said: "I have always believed that the Second Amendment protects the right of individuals to bear arms, but I also identify with the need for crime-ravaged communities to save their children from the violence that plagues our streets through common-sense, effective safety measures. The Supreme Court has now endorsed that view."

FOX News' Mosheh Oinounou and The Associated Press contributed to this report.