Senators Charles Schumer, D-N.Y., and Bob Casey, D-Pa., have unveiled a plan to respond to those like Facebook co-founder Eduardo Saverin, who recently moved to renounce his U.S. citizenship, allegedly to avoid taxes on the profits he is expected to collect from the social networking company’s initial public offering.

Saverin, a partial owner of Facebook, has lived in Singapore since 2009 and renounced his U.S. citizenship in September. The move could help him save a reported $67 million in taxes since Singapore, unlike the U.S., has no capital gains tax. That amount could increase even further as Facebook’s stock price rises. The company went public last Friday, but barely rose above its offering price amid technical problems with the Nasdaq market.

The senators called Saverin’s move an outrage and described a plan to re-impose taxes on expatriates like Saverin even after they flee the United States and take up residence in a foreign country. Their plan would also bar individuals like Saverin from reentering the country so long as they continued to avoid paying their taxes in full.

“Mr. Saverin has decided to ‘defriend’ the United States of America just to avoid paying his taxes. We aren’t going to let him get away with it so easily,” Schumer said in a statement Thursday. “It’s infuriating to see someone sell out the country that welcomed him and kept him safe, educated him and helped him become a billionaire. This is a great American success story gone horribly wrong. We plan to put a stop to this tax avoidance scheme. There should be no financial gain from renouncing your country.”

”We simply cannot allow the ultra-wealthy to write their own rules,” said Casey. “Mr. Saverin has benefited greatly from being a citizen of the United States but he has chosen to cast it aside and leave U.S. taxpayers with the bill. Renouncing citizenship to simply avoid paying your fair share is an insult to middle class Americans and we will not accept it.”

Schumer and Casey’s proposal is called the Ex-PATRIOT Act (“Expatriation Prevention by Abolishing Tax-Related Incentives for Offshore Tenancy” Act).

Under the proposal, any expatriate with either a net worth of $2 million or an average income tax liability of at least $148,000 over the last five years will be presumed to have renounced their citizenship for tax avoidance purposes. The individual would then have an opportunity to demonstrate otherwise to the IRS by meeting specific IRS requirements.

If the individual has a legitimate reason for renouncing his or her citizenship, no penalties would apply. But if the IRS found that an individual gave up their passport for substantial tax purposes, then it would prospectively impose a tax on the individual’s future investment gains, no matter where he or she resides. This would eliminate any tax benefit and financial incentive from renouncing one’s citizenship. The rate of this capital gains tax would be 30 percent, in keeping with the rate that is already applied on non-resident aliens for dividends and interest earnings.

So long as the individual avoids these taxes, they would be inadmissible to the United States forever. The Ex-PATRIOT Act would change current law to ensure such an individual could not re-enter the United States after renouncing his or her citizenship. The Illegal Immigration Reform and Immigrant Responsibility Act of 1996 was intended to bar any such individual from re-entering the U.S. However, this statute was written in a manner that inhibits its enforcement.

In 2011, a record number of 1,780 people gave up their U.S. passports—a dramatic rise from the 235 persons who did so in 2008. Yet no individual has ever been barred from returning to the United States based upon a finding of renunciation of citizenship for tax purposes. Without an immigration bar of re-entry, those thousands of individuals who renounce their U.S. citizenship could simply return to the United States for 60 days per year, without any tax responsibility. The Ex-PATRIOT Act would close the doors of the U.S. forever to individuals like Saverin if they continued to avoid paying U.S. taxes.