http://www.industrialhemp.net/ gives a bill in US congress in 2007, apparently never passed, which would have legalized industrial hemp. Discussion follows, claiming basically it is legal to grow it in Canada+Europe, but in the USA it is illegal unless have special permit which in practice is essentially impossible to obtain (they give evidence of this impossibility). It is not clear to me synthetic rope is better than hemp rope. I mean, you'd naively think growing it is cheaper than synthesizing it. About "WD Smith rope model" it is ok if the inner rope core is untwisted straight fibers, if outer sheath is twisted and/or braided so that tension on rope compresses the rope radially, thus increasing inter-fiber friction, thus preventing break even if all fibers are cut in random locations.