You cannot have a right collectively that you do not have individually. Individual foreigners are barred from spending to sway elections; it defies logic to allow groups of foreigners, or foreigners in combination with American citizens, to fund political spending through corporations. If that were true, foreigners could easily evade the restriction by simply setting up shell corporations through which to funnel their contributions.

Arguably, then, for a corporation to make political contributions or expenditures legally, it may not have any shareholders who are foreigners or federal contractors. Corporations with easily identifiable shareholders could meet this standard, but most publicly traded corporations probably could not.

This may sound like an extreme result, but it underscores how urgently policy makers need to examine these issues with an eye toward drawing acceptable lines. Perhaps we could require corporations that spend in federal elections to verify that the share of their foreign ownership is less than 20 percent, or some other threshold. The Federal Communications Commission, for example, bars companies that are more than 20 percent owned by foreign nationals from owning a broadcast license. At the moment, without a clarifying rule, the only standard that follows the law is a zero-tolerance standard.

If one thing is clear this election season, it is that many voters feel that their voices are not being heard. We should make sure that the voices of citizens are not being drowned out by corporate money. American billionaires already have an outsize influence on our elections. Let’s not cede yet more power to foreign elites.

To that end, at the next public meeting of the Federal Election Commission, I will move to direct the commission’s lawyers to provide us with options on how best to instruct corporate political spenders of their obligations under both Citizens United and statutory law. The American people deserve assurances from American corporations that they are not using the money of foreign shareholders to influence our elections.

Regardless of whether the perpetually deadlocked F.E.C. takes action, lawyers may wish to think twice before signing off on corporate political giving or spending that they cannot guarantee comes entirely from legal sources.

States can also take action, since Citizens United and federal law barring foreign money apply with equal force at the state level. States can require entities accepting political contributions from corporations in state and local races to make sure that those corporations are indeed associations of American citizens — and enforce the ban on foreign political spending against those that are not.

Polls show that overwhelming majorities of Americans reject the conclusions of Citizens United and want to see it overturned. But in the meantime, federal and state policy makers and authorities can at least ensure that corporations are not being used as a front to allow foreign money to seep into our elections.