From the Constitution:

IX. PLAYER LIMITS
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League at-bats for batters is determined by rounding their actual at-bats up
to the next increment of 50.

League starts and appearances for pitchers are limited to their actual number
of starts and appearances, except in the following instances:
        - pitchers with an ERA of 5.01 or greater may double their number of
          starts up to a maximum of 24
        - pitchers with an ERA of 5.01 or greater may double their number of
          relief appearances up to a maximum of 60

All players with at least 200 actual at-bats must accumulate at least 50% of
their actual at-bats as plate appearances, or they will be available in the
rookie draft.

Any overuse of players and/or pitchers will be dealt with individually by the
commissioner.  Penalties may range from a slap on the wrist to title
forfeiture.