From this WaPo story on the latest Clinton administration document dump:

Other e-mails show her immersed in issues that remain relevant today. In 1996, for instance, Kagan articulated the administration’s view that restrictions on campaign spending did not raise First Amendment concerns. That stance would put her at odds with a majority of the current Supreme Court but in agreement with the stated views of Obama. She expressed that view in an e-mail to a colleague, addressing whether only U.S citizens should be allowed to contribute to political campaigns. The counsel’s office, where Kagan worked, was tasked with responding to concerns by the Justice Department and others that such a ban might be unconstitutional.
“This is a result of the Supreme Court’s view — which I believe to be mistaken in many cases — that money is speech and that attempts to limit the influence of money on our political system therefore raise First Amendment issues,” Kagan wrote in an e-mail draft response for Clinton. “The Court could and should approve this measure because of the compelling governmental interest in preventing corruption.”
The draft also said that the court “should reexamine its premise that the freedom of speech guaranteed by the First Amendment entails a right to throw money at the political system.”

It is not clear to me how much this represented SG Kagan’s own thinking vs. her expressing the official position of the Administration.