The government has regularly prevented access to certain websites. It has limited certain websites. It has tried very statutory things. It has tried to introduce systems, with varying degrees of success, where websites had to register with the government. Also it has specifically blocked websites as well. It's uneven, and some external websites do manage to get through to Sri Lanka. Others are blocked and stopped. It's an uneven picture.
The problem is that the overwhelming message from the pro-government media is believed over and above websites anyway, in a sense that the government is able to marginalize websites and just tell lies about them, although on occasion, it also specifically blocks them.