Enforcing patents in preliminary injunction (PI) proceedings in Germany can be a very powerful and efficient means of enforcing patent rights in Germany. In practice they are often the only way to react sufficiently quickly to preserve the innovator's market. This analysis takes a look at the prerequisites for a preliminary injunction, specifically meeting validity and urgency requirements and a change in case-law that means a warning letter must be sent in certain situations before applying for a PI.

German court perspective

Given the potential severe impact on the business of the Respondent, German courts are very strict in issuing preliminary injunctions and there are several prerequisites to consider before applying for one. Apart from a clear case of infringement, the Applicant must demonstrate to the court that the matter is urgent and that the validity of the patent is beyond reasonable doubt. Further, the court has to balance the interests of both parties. While the general prerequisites for a preliminary injunction obviously are the same throughout Germany, there can be significant practical differences between the different venues.

Is your patent strong enough for PI proceedings?

Unlike regular infringement proceedings, the infamous German "bifurcated" system of separate infringement and validity proceedings plays against the Applicant of a PI. In regular infringement proceedings an injunction can be issued if the court finds for infringement and the Respondent is not able to demonstrate that the patent will be held invalid in co-pending validity proceedings with reasonable certainty.1 However, in PI proceedings the burden of proof is practically reversed as the Applicant must convince the court that there are no relevant doubts as to the validity of the patent.

In practice, this requires that the patent already survived an opposition or nullity proceedings.2 Exceptions from this rule apply in some courts where; an in-depth-analysis of the validity is then conducted,3 in pharmaceutical cases of innovator against generics manufacturers4, and under certain circumstances where the patent at issue is bound to expire within a timeframe in which an ordinary first instance procedure will likely not be concluded.

If the validity of the patent was confirmed by either the EPO/German PTO or the German validity courts, the patent is considered "fit" for enforcement via preliminary injunction (even if that validity decision is not final and under appeal). Infringement courts should, therefore, not deny a PI for reasons of validity unless the validity decision is obviously wrong or there is new – previously unconsidered – prior art that renders the invalidation of the patent probable.5

Don’t delay in bringing proceedings!

Of course, the main goal of PIs is to obtain a quick decision. Hesitation or delaying tactics can endanger the grant of a PI for demonstrated lack of urgency on the part of the patentee. The matter of urgency is assessed by the courts on a case-by-case basis. Courts will deny a preliminary injunction for urgency reasons, if the rights holder waits too long to take legal action. The patentee's own conduct should thus not give rise to the impression that he does not proceed as reasonably quickly as he can in order to determine infringement and gather any evidence he needs for a successful PI request.

Although there is no time limit stipulated by law, German courts have established an emergency period of about one month from the time that the patentee obtains knowledge of the infringement. If possible, the patentee should not wait until the last day of this period, though. Some recent case law is examined below in which a PI can also be filed later than four weeks after knowledge of the infringement:

  • Risk of first-time and recurrent infringement

According to Sec. 139 (1) of the German Patent Act, a claim for patent infringement requires that there is either a risk of recurrent infringement or at least one of first-time (imminent) infringement. In this context if a PI brought within the one month time limit after knowledge of an actual infringement (which might be long after having knowledge of a threat of infringement, i.e. imminent or first-time infringement) is it acceptable under the urgency requirement? It has been held that the actual first infringement on which the danger of recurrent infringement is based, sets off a new urgency period as the patentee must wait for an infringement.6 Otherwise, the patentee would be forced to act based on threat of infringement, already. This would also not serve procedural economy given proceedings could be prevented in cases where an actual infringement never occurs. Thus, the risk of the first time infringement entitles the patentee to bring suit, but may not oblige him to file a motion for a preliminary injunction. Case-law on this question is not settled, however, and courts have indicated that they might decide differently depending on the circumstances of the individual case. The patentee thus is well-advised to bring his request for a preliminary injunction earlier rather than later.

  • Waiting for the written reasons (invalidity decisions)

As set out above, it is generally accepted that a patent is only "fit" for enforcement if it has survived at least an instance of a validity procedure. It is thus safe to assume that the urgency period does not start until the decision on validity is made. Further thought needs to be given to the question, though, whether the patentee should wait not only for the decision but for the written grounds of that decision –usually issued several months after the actual decision. In certain circumstances – for example where claim interpretation depends on the arguments of the EPO opposition division or the German Federal Patent Court – waiting for the written grounds may be justified. However, the patentee must not wait for the written grounds of the appeal decision.7 As the decision is final and there remain no doubts about the final result of the procedure, immediate action is required.

  • Changes in case law

There might be situations in which a change in case law may for the first time improve the chances of successful claim for patent infringement. This may then initiate a new emergency period.8 However, the patentee has to draw its own legal conclusions based on the case law and may not wait for e.g. legal commentary to back this up (or for a subsequent decision of a court applying this case law). Based on this exception, one has to act within one month  after the new case law becomes known. The patentee thus bears the risk of an incorrect assessment.

Make use of warning letters

Until recently, writing warning letters to a potential Respondent was not a prerequisite under German law. Rather, sending warning letters always brought the risk of liability for unjustified warning letters and often yielded unsatisfactory replies.

However, following two decisions of the German Constitutional Court,9 issuing an ex parte PI in patent law violates the Respondent’s right to procedural equality, an equivalent to a fundamental right, if the Respondent was not involved or heard. Accordingly, it is now advisable, if not a prerequisite, to send a (soft) warning letter to the Respondent, first, and supplying this and his reply to the court when applying for an ex parte PI. Without having sent a warning letter, obtaining a PI will only be possible in cases where the Respondent's right to be heard is observed in some other form prior to issuing the injunction. The Respondent may have, for example, filed a protective letter, where notice to the Respondent would run counter to the reasonable interests of the Applicant, e.g. if the purpose of the proceedings would otherwise be thwarted (because the Respondent could destroy evidence, in requests for a seizure at a trade fair, etc.) or in inter partes proceedings. This needs also to be kept in mind when filing a protective letter which might in some circumstances actually allow an ex parte PI to be issued against the Respondent.

A further consequence of the decisions by the constitutional court is that the courts need to take notes about discussions with the Applicant's lawyers and notices given. When a PI request is finally denied in ex parte proceedings, the court might inform the Respondent about the failed attempt at obtaining a PI and can also share its notes with the Respondent's lawyers. It thus needs to be kept in mind that the other side can – in contrast to previous practice – be made aware of a failed attempt at obtaining a PI.

Involve stakeholders early to prevent PI enforcement delays

With regard to the potential damages that might be caused by an enforcement of a PI which is later lifted as unfounded, courts often require the patentee to provide a substantial security before the decision can be enforced.10 The security is typically provided by way of a bank bond. In practice, it may take some time to agree to a sufficient credit line with a German bank, to agree the specific text of the bond document which needs to comply with prerequisites set out in case-law and which sometimes seems unusual to banks, and to finally get the bond issued. It is thus advisable to start early with preparation of a potential bond to prevent delays in the enforcement of the decision.

Next steps

Enforcing a patent via preliminary injunction proceedings can be a powerful method to quickly secure a market position. It should however be carefully planned and steps should be taken so that evidence can be gathered quickly and proceedings can be brought well within the time limit applied by the courts. Following recent developments, it is further advisable to send a soft warning letter with a short deadline for reply to the Respondent before bringing the request for grant of an ex parte preliminary injunction.

We have in-depth experience with preliminary injunction proceedings and can help you preparing to defend your market share against competitors or to defend against potential preliminary injunction requests. Please contact us for tailored assistance.


1.               German Federal Supreme Court, GRUR 2014, 1237 Rn. 10 – short messages ("Kurznachrichten").

2.               Higher Regional Court Düsseldorf, BeckRS 2017, 125978 Rn. 64 with further references.

3.               Higher Regional Court Munich, 6 W 164/18, judgement of 4 April 2018.

4.               Higher Regional Court Düsseldorf, GRUR-Prax 2018, 173 (Dorn); Higher Regional Court Düsseldorf, BeckRS 2013, 04162 - Flupirtin-Maleat.

5.               E.g. Higher Regional Court of Dusseldorf, I-2 U 28/19, judgment of 26 September 2019.

6.               Regional Court Munich I, PharmR 2016, 432.

7.               Higher Regional Court Düsseldorf, GRUR-RR 2017, 477 – vacuum-based treatment system ("Vakuumgestütztes Behandlungssystem")

8.               Higher Regional Court Düsseldorf, GRUR 2017, 1107 – estrogen blocker ("Östrogenblocker").

9.               BVerfG, 1 BvR 1783/17 and 1 BvR 2421/17.

10.              E.g. Higher Regional Court Düsseldorf, BeckRS 2019, 14699 Rn. 53/PharmR 2019, 546.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.