Teams own "reserve rights" to all players from their teams as determined by having the highest number of games played in that uniform.( Players who played the most games for a team not represented in the league cannot be claimed, and will enter the draft "at large".)
Franchise owners will have a chance at the beginning of each round to execute claims on as many of their players as they like, spending their team's next draft picks sequentially (highest first) to do so. This will make for interesting calculus about how much guys are worth relative to pick positioning in the round, how far they’re likely to fall, etc. In the long view, this mechanism should facilitiate occasional "bumper crops" of players for each team through the league's progression. If Ted Williams and Roger Clemens come out in the same year, the Sox will get them both.
Reserve rights are not attached when draft picks are traded away. Picks traded away are "at large," and cannot be used for reserve claims by the recipient team. The team trading the pick still has reserve rights before each round, and is able to claim as many players as they have picks remaining.