I found this website when digging into some old acts of Sri Lanka. The site appears containing lot of valuable information.
Commonwealth Legal Information Institute website declares that it has 981 databases from 59 Commonwealth and common law jurisdictions via 8 Legal Information Institutes.
This is the direct link to the Sri Lanka page.
It seems so easy to handle and look at this page from where you can access, I believe, all numbered parliamentary acts from 1956 to 2006.
Here is the Constitution of the Democratic Socialist Republic of Sri Lanka.
It has lot of links to websites of Sri Lankan origin but some I tested did not download.