Objection of invalidity: Most common defense strategy in infringement proceedings; the protective effect of a patent extends only as far as it is legally valid.

Grounds for invalidity: Lack of novelty, lack of inventive step, lack of feasibility, or inadmissible extension.

Limitation in proceedings: Patent holder may file auxiliary requests to save the patent by limitation; extension of the scope of protection is inadmissible.

Division of proceedings: In Austria and Germany, separate jurisdiction (infringement → civil courts, nullity → Patent Office/Federal Patent Court); in other countries (e.g., Spain), the same court decides. civil courts, nullity → Patent Office/Federal Patent Court); in other countries (e.g., Spain), the same court decides.

Protection gap: While the infringement proceedings are suspended due to an open nullity issue, the defendant can continue to distribute the contested product.

Preliminary injunction: Option for the patent holder to close the protection gap; however, this carries a risk, as there is a threat of damages for unjustified preliminary injunction in the event of subsequent nullification.

Completely null and void → Action is dismissed; patent is retroactively deemed never to have existed.

Partially invalid → Patent remains in limited form; infringement court examines whether this form is still infringed.

Fully valid → Plea of invalidity fails; infringement proceedings continue, claims for injunctive relief and damages remain in full force.