The grant of the patent is published in the Patent Gazette, which gives the patent legal effects (Sec. 58 I Patent Law). 

The term "effect" refers to the rights of use and prohibition to which the right holder is entitled on the basis of his property right. The effect of the patent may be direct or indirect. The direct effect is, that in the absence of the consent of the proprietor of the patent, any third party shall be prohibited from

• producing, offering, putting on the market or using a product which is the subject-matter of the patent, or from either importing or possessing such a product for the purposes referred to;

• using a process which is the subject-matter of the patent or, if the third party knows or if it is obvious from the circumstances that use of the process is prohibited in the absence of the consent of the proprietor of the patent, from offering the process for use within the territorial scope of this Act;

• offering, placing on the market or using a product which is produced directly by a process which is the subject-matter of the patent, or from either importing or possessing such a product for the purposes referred to.

If a third party infringes your patent, you are entitled to some claims. 

The most important claims in practice are the right to injunctive relief, the right to destruction and the right to information about the origin and channels of commerce of the goods infringing your property right. If the infringer acts intentionally or negligently, he is also obliged to compensate you for the damage resulting from the infringement. 

First of all, it must be carefully examined whether it is actually an infringement of property rights and how legally valid the own property right is. An attack based on an obviously legally unstable property right or an attack if there is no property right infringement at all can, in the worst case, lead to the fact that one makes oneself liable for compensation towards the alleged infringer. 

If there is any doubt as to whether an infringement of property rights has occurred, it is advisable to make an authorisation enquiry. With the authorisation enquiry, the alleged infringer is requested to comment on the suspected infringement, whereby the request is only aimed at an exchange of opinions with the potential infringer and not at direct enforcement of the law. The information provided should enable the property right owner to assess whether or not the conduct identified constitutes an infringement of property rights.

If there is an infringement, it is advisable to check whether the matter can be settled out of court before going to court in order to save time and money. The means of choice is then to issue a warning and to negotiate a cease-and-desist declaration with the other party with penalty. If the case does end up in court, one is usually no longer affected by the cost case of the assault action according to § 93 ZPO (German Code of Civil Procedure), according to which the plaintiff shall bear the costs of the proceedings should the defendant immerdiately acknowledge the claim and has not given cause for an action to be brought. This means that you would have to bear the legal costs and attorney's fees for yourself and the infringer if you did not warn the infringer prior to the action. This is because the acknowledgement of the infringer makes it clear that the lawsuit was not necessary and could have been avoided by choosing a milder means. 

A warning with a cease-and-desist declaration subject to a penalty is intended on the one hand to inform about the infringement (warning) and at the same time to eliminate the risk of repetition (cease-and-desist declaration). The warning notice can also be used to assert further claims, e.g. a claim for information.

With a cease-and-desist declaration subject to a penalty, the person making it undertakes to refrain from certain unlawful conduct or a measure complained of in the future. 

If the infringing party makes this declaration, the risk of repetition of the infringing act has been eliminated from a legal perspective and legal peace has been restored.