What to do next
Common situations
A competitor launches a product that appears to work the way yours does. A former manufacturing partner begins selling a similar item. An importer brings in an equivalent product from overseas. A licensee continues using the technology after the licence ends. The last of these is often a contract claim as much as an infringement claim, and is usually the fastest to resolve.
Get a claim construction and infringement analysis first
Infringement is assessed against the wording of your claims, not against your commercial product. A patent lawyer or agent will map each claim element to the accused product. If a single element is absent, there may be no literal infringement - which is why this analysis comes before any letter is sent.
Assess your own validity honestly
Expect the other side to search for prior art and challenge validity, whether in court or through an administrative proceeding. Reviewing your prosecution history and the prior art landscape before asserting is the difference between negotiating from strength and losing the patent.
When to speak with a lawyer
Before sending anything. An unjustified infringement threat can expose you to a claim in some jurisdictions, and a poorly drafted letter can start a limitation clock or invite a declaratory action in a forum you did not choose.
Types of lawyers who handle this
A patent litigator, usually with a registered patent agent for the technical claim analysis. Where the product is imported, customs and border measures may involve trade counsel; where a licence is in issue, commercial litigation experience matters.
What to prepare
The patent and its prosecution history, evidence of the accused product that you can lawfully obtain - public listings, marketing material, a purchased sample, published specifications - your own commercialisation and licensing history, and a timeline of when you first became aware. **Obtain product information through ordinary lawful means only**; do not attempt to acquire a competitor's internal technical documents or access their systems.
Possible legal pathways
Negotiation or a licence, a cease and desist where the analysis supports it, administrative validity or opposition proceedings, customs recordal for imported goods, and litigation. In Canada patent actions go to the Federal Court or a provincial superior court; in the United States they start in a district court and all appeals go to the Federal Circuit, which is why US patent law is national.
Frequently asked questions
Does my Canadian patent protect me in the US?
No. Patents are territorial. Enforcement requires a patent in each country where you want protection, which is why filing strategy and enforcement strategy are connected.
Will asserting my patent put it at risk?
It can. Validity challenges are a standard response, in court and through administrative proceedings. Assess your prior art position before asserting, not after.
Can I just send a cease and desist?
Take advice first. An unjustified threat can expose you to a claim in some jurisdictions, and a letter can trigger a declaratory action in a forum the other side prefers.
How long do I have?
Limitation periods apply and vary by jurisdiction, and ongoing infringement can affect what is recoverable. Delay can also weaken a request for interlocutory relief.
Which court handles patent cases?
In Canada, the Federal Court or a provincial superior court. In the United States, a federal district court, with all appeals going to the Court of Appeals for the Federal Circuit.
This is general information, not legal advice. Laws vary by location and every situation is different — speak with a qualified lawyer about your specific circumstances.