Is a patent valid in all the countries?

No, patent rights are territorial rights. In general, the exclusive rights are valid only in the country or region in which a patent has been filed and granted as per the law of that country or region.

On the initiative of the right owner, patent rights are enforced in a country. A court of law has the authority to stop patent infringement. It is the responsibility of the patent owner to monitor, identify, and take action against infringers of a patent.