Can you do reactions on a movement from base to a battlefield that's already under your control?

Ruling: Whether you can react to a movement depends on how the movement was performed and whether anything triggers during the movement.

Sequence:

• If the movement was done via Standard Move and nothing triggers, no chain opens and you cannot react
• If the movement was done through a spell or activate ability, a chain opens and you can react
• If any effect triggers while moving (regardless of how the movement was performed), that effect opens a chain and is reactible

Nuances:

• Standard Move by itself does not open a chain
• The method of movement (Standard Move vs spell/ability) determines whether a chain opens
• Triggered effects during movement always open a chain even if the movement itself wouldn't