This has a lot of good and bad potential, depending on how it used and what for.
On one hand being able to legitimately go after people mass producing fake products that people are buying unknowingly (big in Hong Kong) is a good thing. They would not be able to use being in another country as an excuse to avoid punishment.
On the other hand being ability to confiscate generic medicine and potentially fine people who are buying it (such as people buying cheaper medicine in Canada because they are unable to afford it in the US, which is usually the same thing but considerably marked up) seems silly.
Being able to go above the U.S. court systems and levy punishments to people is where it gets a little scary.
In a court ruling if people do not like a decision made they can appeal, voice concerns, run petitions, elect different officials to vote on amendments, et cetera. But since this is considered a treaty the only one really having any say is the President. So if there is a ruling in the future and the court ruling is a person was within their rights to post something fake on line the countries that are a part of this treaty could potential say I do not think so and still punish the person regardless of the individual country's ruling.
It is a step towards global law, which I can understand because information and the economy are now global entities. I do not know all the facts about this but it is odd that there appears to be a good deal of secrecy surrounding it.
There is a
wikipedia article, a
UK perspective, and an
educated breakdown to help people get more information on it.