What alternative rules did Chief Justice Roberts suggest instead of aggregate contribution limits?

In the case of McCutcheon v. Federal Election Commission, Chief Justice John G. Roberts, Jr. argued that aggregate contribution limits were unconstitutional because they were not "closely drawn" to prevent corruption and unnecessarily abridged First Amendment rights. He suggested that Congress could instead utilize more targeted alternatives to address concerns regarding the circumvention of base contribution limits.1

These suggested alternatives included:

• Targeted restrictions: Implementing specific limits on transfers between party committees and on transfers from candidates to party committees, which were previously unlimited.1
• Tightened earmarking rules: Strengthening existing regulations to prevent donors from effectively directing contributions through political action committees (PACs) to a single candidate.1
• Broad disclosure requirements: Enhancing transparency mandates to expose large contributions and expenditures to public scrutiny, which serves to deter actual corruption and mitigate the appearance of corruption.1

Roberts maintained that these measures would serve the government's interest in preventing circumvention without imposing the significant First Amendment costs associated with aggregate limits.1