For the USA at a federal level - none, since it was still kept legal. The 1937 act distinguished between drug hemp (illegal) and industrial hemp (legal). Some states made industrial hemp illegal, others didn't go to the trouble.
Industrial hemp still failed to be competitive even in the states that kept it legal. Large-scale usage had stopped by the 1950s or thereabouts. If I remember properly, later federal acts didn't bother to distinguish between different kinds of hemp because there was no longer any significant commercial use of industrial hemp.