There’s a good chance Congress will consider legislation this summer to extend trade promotion authority (TPA) to President Obama. If it does, lawmakers should pay especially close attention to the wording of the bill.

TPA is the legislative vehicle that allows the President to negotiate with other countries on beneficial trade agreements. The purpose of trade promotion authority is, obviously, to promote trade. If properly designed, TPA is an effective way to expand trade and economic freedom. However, a poorly worded TPA bill could allow implementing legislation for future trade agreements to be used for other purposes.

For example, under the last extension of TPA, Congress agreed to consider legislation that implemented trade agreements negotiated by the President on an up-or-down vote. This implementing legislation could include changes in laws that were “necessary or appropriate to implement such trade agreement or agreements, either repealing or amending existing laws or providing new statutory authority.”

When the South Korea–U.S. free trade agreement (KORUS) came up for a vote two years ago, the Obama Administration used this language as justification to try to attach Trade Adjustment Assistance (TAA)—which provides federal aid to those supposedly hurt by trade—to the implementing legislation for KORUS. At the time, TAA supporters argued that such assistance was “necessary and appropriate.”

Trade expert Phil Levy observed at the time that TPA “was hard to come by even in the best of circumstances. What chance would it have now, if it is interpreted as giving any White House the right to attach controversial and unrelated spending measures in a protected way?”

This is exactly why it is important to clarify how TPA works. Every U.S. President should have the authority to negotiate beneficial trade agreements. However, TPA was never intended to be a blank check. Congress should make it clear that future trade agreements submitted for implementation under TPA cannot be hijacked as a vehicle on which to attach extraneous provisions.