>>64781301American teams are bound to it because MLB agreed to it as well. Japanese players are not defecting like Cubans, nor are they free agents - they are contractually bound to play for their NPB teams like MLB players are. Like MLB players, they can earn free agency based on playing time. Domestic free agency is generally earned after seven years, and international free agency after nine. Hisashi Iwakuma, Kosuke Fukudome and Tsuyoshi Wada are all examples of players who signed with MLB teams as free agents after earning their international FA status, meaning they circumvented the posting system and negotiated directly with their own MLB teams.
The posting system, fundamentally, is designed to keep Japanese players in Japan and protect the NPB from having the player assets that it developed poached by MLB teams with more money. On the one hand, this makes sense - the loss of Darvish and Tanaka, for example, were huge hits in the league's marketability domestically and their teams therefore deserved to be financially compensated for that loss. On the other hand, the posting system - especially before it was revised in 2012/2013 - took almost all right out of the hands of the players themselves, and ensured that they would almost certainly earn less in America than their talents allowed for. This is because the open-market bidding phase of the posting process determined how much money the player's team would be paid, not the player himself. Iwakuma's failed posting is a great example of the flaws of this system - Oakland won the bidding, but refused to sign Iwakuma to a market-level contract since they'd already paid for the right to negotiate with him. Iwakuma went back to Japan, the A's got their posting money back, and Iwakuma came over to Seattle a year later as a free agent. The posting system was then overhauled before Tanaka's posting - essentially, the Japanese team receives only a maximum of $20M posting fee, and teams who are willing to pay that are free to compete to offer the player the highest contract. This is better for the player, since it allows him to better test the market while still giving some compensation to the Japanese team for giving him up.
