Whats the maximum age to be on parents' health insurance?

I ask this because I know the law has changed to the age of 26 all around but has this taken effect?
--------------------
After September 2010 dependents will be able to stay on their parents health insurance through age 26. Check with your health insurance carrier to see how they plan on implementing the change. I understand some companies are allowing this policy change now but others might not make the change until the following renewal.
Source