Can you assign combat damage to a planeswalker without the attacking player choosing to redirect it?

Prior to a rules change in 2010, combat damage to planeswalkers required a 'redirect' from a player's life total. That rule no longer exists. Under the current Comprehensive Rules, a planeswalker is a legal attack target in its own right (CR 508.1), so an attacking creature can be declared as attacking a planeswalker directly during the declare-attackers step.

When a creature attacks a planeswalker, combat damage is assigned to that planeswalker just as it would be assigned to a player or a blocking creature. The attacking player never needs to 'redirect' anything — the damage simply goes to the planeswalker (CR 510.1, 510.2). Excess damage is not redirected to the planeswalker's controller unless a special ability says so.

Loyalty counters are removed equal to the damage dealt, and if the planeswalker has zero or fewer loyalty counters after the damage resolves, it is put into its owner's graveyard as a state-based action (CR 306.9, CR 704.5i).

Example: Your opponent controls Liliana of the Veil with 4 loyalty counters. You attack with a 3/3 creature targeting Liliana directly. No redirect choice is made — the creature deals 3 damage to Liliana, removing 3 loyalty counters, leaving her at 1 loyalty.

Note: A creature attacking a planeswalker can still be blocked normally. Blockers deal damage to the attacking creature, not to the planeswalker, unless an ability specifies otherwise (CR 509.1).