Official rule text
16 If a player’s space docks are in the same system as another player’s ships, those space docks are blockaded. Blockaded space docks cannot produce ships. They may, however, still produce ground forces. KEY CONCEPT: SPENDING RESOURCES AND INFLUENCE Many effects in Twilight Imperium require a player to spend resources or influence. To spend a planet’s resources or influence, a player exhausts that planet’s planet card. For example, if a player needs to spend two resources to produce units, that player can exhaust a planet that has a resource value of “2” or instead exhaust two planets that each have resource values of “1.” The player could exhaust a planet that has more resources, but the excess resources are lost. 5. PRODUCTION The active player can produce units using their space docks in the active system. When a player produces units, they may choose to produce any of the units on their faction sheet by spending resources equal to the chosen unit’s cost. When a unit is produced, the player takes the unit from their reinforcements and places it in the active system. Players always place ships in the space area of the system in which they were produced. Players always place ground forces on the planet that contains the space dock that produced them.