According to United States law, you can't patent algorithms for the same reason that you can't patent blueprints, i.e., patents apply to useful inventions, to things that work in the world, as opposed to abstract ideas.

To get a sense of the distinction, it may be helpful to think about the Supreme Court's *other* big patent ruling today, i.e., Microsoft v. Alcatel-Lucent. In this case, both companies admitted that Windows infringes on Lucent's speech recognition patents. Normally, these patents would not apply to products in other countries, which are governed by their own patent laws. This explicitly includes cases in which somebody sells a blueprint to somebody else in another country, who then uses that blueprint to manufacture a product that infringes on a US patent. The exception in US law is if you ship components of an infringing product overseas and then have them assembled over there. Congress correctly perceived such an act as an attempted end-run around US patent laws and said that, whether or not it is assembled in the US, a product that is manufactured in the United States and infringes on US patents is subject to US patent law.

Microsoft ships a master DVD overseas, where it is duplicated and installed on computers there. Alcatel-Lucent argued that this is fundamentally similar to assembling a US-manufactured product overseas and that Microsoft should pay damages. (A lower court awarded them $1.5 billion.) Microsoft argued, however, that shipping a master DVD is more like sending a blueprint for products that are then manufactured overseas. The Supreme Court concurred, ruling in favor of Microsoft 8-1.

Now here's the key twist. In an Amicus brief that was probably not appreciated by Microsoft and apparently not embraced by the court, the SFLC argued that *all* software is like a blueprint or an algorithm, as this weird test case of installing it overseas versus installing it domestically demonstrates (in their view). Therefore, software should be fundamentally unpatentable.