Free mobility of labor.
But it is most likely under an FTA no set asides are allowed.
We call these things Free Trade Agreement because the eliminate tariffs or harmonize tariffs and harmonizing makes the tariffs self canceling.
But they are really Investor State Trade Agreements. And since the disputes are settled by the arbitration panels, the arbitration panels, over time, are making rulings which develops a body of law(by precedent) which becomes known as Investor State Law.
Do a Google Search of "Investor State Trade Agreement" and/or "Investor State Law"
The premise of this is that an investor can make a deal with the state in which the investor is protected from future taxes by the state.
But the state may try to get around this by implementing regulations/protections for labor, environment, or social welfare. These would be taxes masquerading as regulations. So the investor has to be protected from these by investor protections. In the case of NAFTA, the investor protections were found in Chapter 11.
Some of the big cases that came out of NAFTA were MetalClad, Methenex, and the Canadian Softwoods dispute in which the Canadian Provincial govts were subsidizing their timber industry and workers with low stumpage fees to the detriment of US timber companies.
But, when you implement these investor protections, there is always the possibility that labor or environment will get a bad deal.
Which is why the unions are bashing Obama over the TPP. They say TPP is going to be worse than NAFTA or CAFTA.