On 16 September, President Obama signed into law the America Invents Act, which will mean the United States will use a "first inventor to file" system instead of a "first to invent" system to determine which patent applications hold the most merit, bringing it in line with other developed countries. It will also provide a nine-month window for inventors or companies to contest a patent after it is granted.
One of the changes brought in by the America Invents Act is the effect of a claim to foreign priority under the Paris Convention. Until now, the priority date did not count as the effective filing date for 35 USC 102(e).
The practical effect of this has been for many applicants outside the US (in particular patent departments of subsidiaries of US corporations) to first file in the USPTO or to directly file PCT applications to establish an actual date of filing for the US, rather than to rely on a priority date established in a national office.
The new act strikes out the provision of 35 USC 119(a) that confers this advantage on applicants for US patents.
It means that as between, for example, (A) an application for a US patent filed on 1 July 2011 and (B) an application for a UK patent filed that day and subsequently filed a year later in the USPTO, once a patent is granted in each case, that patent has a prior art effect dating back to 1 July 2011. In contrast, until now, someone filing a patent application later than 1 July 2011 (before publication of either earlier application) could "swear behind" the US filing date of B (but not of A).
This is good news internationally. It means there is no longer any vestige of a disadvantage from using the Paris Convention. There is no disadvantage in the simple and cheap option of filing a UK patent application (for example) to establish a date of priority. Applicants can take advantage of the full Convention year to decide whether to file a PCT application or a US patent application.