The laws of thermodynamics alone lead me to suspect that that's probably not the case.

The energy input to crops that later become ethanol is the sun, not the gasoline burnt in the production process, so there is no necessary relationship inferrable by thermodynamics between fuel burnt and the energy content of crops or the resulting ethanol.

If there were, then human-powered farming would have been pointless as a food production method.

I assume you're speaking in theoretical terms, but it bears mentioning that in practice, fossil fuels are a critical input to the production of crops, to the extent that EROEI for corn ethanol remains stuck at around 1.

I stand corrected.