Enforcing the Rules


The New York Times reports that contributions to a new breed of super-advocacy groups might start getting taxed:

Big donors like David H. Koch and George Soros may owe taxes on their millions of dollars in contributions to nonprofit advocacy groups that are playing an increasing role in American politics.

….The organizations in question were established as nonprofit corporations under a section of the tax law, 501(c)(4), and the rules governing them say their primary purpose cannot be political. Unlike contributions to charities, however, donations to these groups have always been subject to a gift tax. But tax experts and campaign finance experts say the I.R.S. had not enforced that rule, until now.

I’m confused. Why hasn’t the IRS enforced this rule until now? Isn’t its job enforcing tax rules?