Two Republicans in Congress — Oklahoma senator James Lankford and North Carolina representative Robert Pittenger — are teaming up to crack down on potential abuse of tax-exempt municipal bonds, which some cities and states have chosen to issue to abortion providers for the purpose of building new clinics.

The Hyde Amendment has been attached to federal spending bills since the mid 1970s to prevent taxpayer money from funding abortions, but these Republican legislators say they’ve found a loophole in the tax law that permits tax-free municipal bonds to entangle federal money in the process of creating new abortion clinics.

In a joint letter sent this morning to the U.S. comptroller general, Lankford and Pittenger cite a few examples of this practice having taken place in recent years. In 2012, for example, New York City issued a tax-free $15 million municipal bond to renovate Planned Parenthood’s national headquarters, which the group later sold for nearly $70 million, doubling the amount it initially paid for the location

Meanwhile, in both Florida and Illinois, counties gave Planned Parenthood clinics $8 million tax-free bonds to fund the construction of new clinics to provide abortion services. In response, Lankford and Pittenger are requesting a full report on instances of such bonds being issued, a list of states that issued them, the resulting federal tax liability, and the effect of the bonds on each abortion provider.

Last summer, Lankford cosponsored a bill with Senator Cory Booker (D., N.J.) to cut wasteful spending by ending federal tax subsidies for the construction of professional sports stadiums. This new effort with Pittenger is a similar endeavor to reduce federal tax liabilities, but it is also motivated by both congressmen’s belief in conscience rights and opposition to abortion.