Another development in the ongoing story of how Eduardo Saverin has given up his U.S. citizenship to avoid paying $67 million in taxes related to Facebook’s IPO: the U.S. government doesn’t want him get away with it quite so fast.

Today, Senators Charles Schumer and Bob Casey are expected to announce a plan they have to re-impose the taxes on Saverin, part of a bigger scheme to go after expatriates who give up citizenship in order to avoid taxes. On top of that, they want to make it official that people who avoid paying their taxes by renouncing citizenship will be permanently denied re-entry into the U.S.

The plan, the offices of the two Senators said, will be announced today at 11am Eastern in a press conference at the Senate Radio-TV Gallery in the U.S. Capitol building.

Called the “Ex-Patriot” act (short for “Expatriation Prevention by Abolishing Tax-Related Incentives for Offshore Tenancy”, according to ABC News), the act proposes to re-impose a mandatory 30 percent tax on the capital gains of anyone who renounces citizenship — even if they are no longer resident in the U.S.

In Singapore, where Saverin currently resides, individuals do not need to pay capital gains taxes, so it’s thought that Saverin is using his residency there to avoid paying a minimum $67 million tax bill — more if the share price rises — on shares that he sells in Facebook after the company is expected to IPO tomorrow. He is expected to make $3.84 billion once Facebook goes public. Saverin has lived in Singapore since 2009 and renounced his citizenship in September 2011.

It’s not clear how many other ex-pats might be liable for such hefty bills if the act gets passed. Facebook, which is expected to raise at least $16 billion in the IPO, is one of the biggest IPOs of all time and is getting an extra level of scrutiny as a result, with the debate ranging from accusations of Saverin being plain wrong in his approach and others, if not exactly supporting him, pointing out the other side of the debate and how he’s just being a good old, gambling capitalist.

Well, Schumer (D-NY) and Casey (D-PA) are mad as hell and they’re not going to take it anymore. They will call Saverin’s $67 million tax “duck” an “outrage” today in their press conference when they detail the rest of the Ex-Patriot act.

Update: More details on the Ex-PATRIOT Act in a new post here.