"Many folks are stating this was a clear-cut case of violation of contract law"
Those people are wrong. Monsanto did, indeed, sue him for patent infringement, not breach of contract. The contract mentioned in the case is just his license to grow the plants from Monsanto. He was forbidden from replanting those soybeans (or other patented soybeans) by patent law because such actions exceeded the scope of his license. There is nothing at all in the opinion that refers to a contract where he agreed only to buy RR soybeans from Monsanto.
Those people are wrong. Monsanto did, indeed, sue him for patent infringement, not breach of contract. The contract mentioned in the case is just his license to grow the plants from Monsanto. He was forbidden from replanting those soybeans (or other patented soybeans) by patent law because such actions exceeded the scope of his license. There is nothing at all in the opinion that refers to a contract where he agreed only to buy RR soybeans from Monsanto.