Why focus the judgment on 'His people'? What's so special about their case?
The verse specifically states that God calls the heavens and earth 'that he may judge his people.' This isn't a judgment of the entire world in this instance, but a focused reckoning within God's covenant community.
The Privilege and Responsibility of Covenant
Because Israel (and by extension, believers today) stands in a special relationship with God, their actions carry immense weight. They have received God's revelation, His law, and His grace. Therefore, their failures are seen not just as personal sins, but as betrayals of a sacred covenant.
A Higher Standard
This implies a higher standard for those who claim God as their own. God's judgment on His people is often corrective, aimed at purification and restoration, rather than pure condemnation (though condemnation is the outcome for unrepentant sin). The cosmic witnesses ensure that the justice of this scrutiny is evident to all.