Owners of registered intellectual property rights in the United Kingdom can call in aid many weapons that can be fired against the actual, putative or potential infringer -- interim and permanent injunctive relief, damages, an account of profits, delivery up and declarations. The defendant in turn can seek a declaration of invalidity or the cancellation/revocation of the registered right and may in an appropriate situation bring an action for unwarranted threats to bring infringement proceedings against him.
In the case of copyright the defendant's position appears more vulnerable. Damages which he may be required to pay explicitly include additional ('exemplary' or 'punitive' damages) -- though the effect of the EU's IP Enforcement Directive 2004/48 may be that such damages should be available in respect of all IP rights -- and there is no opportunity to challenge the validity of a registration. He also faces the risk that the copyright owner will opt for self-help relief where the statutory conditions are satisfied and simply seize goods believed to infringe and then walk off with them. More worryingly, in light of recent heavy-handed attempts to discourage or punish file-sharing and unlawful downloading, is the fact that there is no unwarranted threats action which an innocent but threatened party can bring.
Does any reader know quite why an action for unwarranted threats has not been made available in the case of a threat to bring copyright infringement proceedings? It can't be because the right in question is an unregistered right, because an action for unwarranted threats exists in respect of UK unregistered designs right under section 253 of the Copyright, Designs and Patents Act 1988, and a comparable provision exists for unregistered Community design right.