Short answer. Five grounds. Rule 39 lets you repel a foreign judgment or final order with evidence of a want of jurisdiction, want of notice to the party, collusion, fraud, or clear mistake of law or fact — outside those grounds, the foreign judgment stands as conclusive or presumptive evidence against you.
What the law says
the judgment or final order may be repelled by evidence of a want of jurisdiction, want of notice to the party, collusion, fraud, or clear mistake of law or fact.
Rule 39, Section 48 — Effect of foreign judgments or final orders. Read the full provision →
What a foreign judgment normally establishes here
Rule 39, Section 48 gives a foreign judgment real weight in the Philippines by default. In case of a judgment or final order upon a specific thing, the judgment or final order is conclusive upon the title to the thing; and in case of a judgment or final order against a person, the judgment or final order is presumptive evidence of a right as between the parties and their successors in interest by a subsequent title. A judgment on title to property binds outright; a judgment against a person is presumed correct unless successfully challenged.
The five grounds that let you repel it
Whichever category the judgment falls into, the same escape route applies: the judgment or final order may be repelled by evidence of a want of jurisdiction, want of notice to the party, collusion, fraud, or clear mistake of law or fact. These five grounds — jurisdiction, notice, collusion, fraud, and clear mistake — are what you would need to present evidence of to keep the foreign judgment from being treated as conclusive or presumptive against you.
The foreign court had to have jurisdiction to begin with
The rule's own opening line already builds in a threshold condition: it applies to a judgment of a tribunal of a foreign country, having jurisdiction to render the judgment or final order. This overlaps with, but is not identical to, the "want of jurisdiction" ground for repelling the judgment — the rule effectively requires proper jurisdiction on the front end, and separately lets you attack a lack of it after the fact.
Whether the judgment concerns a thing or a person
It matters which of the two categories your case falls into, because the presumption you are fighting differs. A judgment on title to a specific thing is conclusive, a stronger presumption to overcome, while a judgment against a person is only presumptive evidence, a comparatively lighter starting point. Either way, the same five grounds are what the rule gives you to work with, whichever kind of judgment is actually being enforced against you.